ABC of WCF

WCF Service is a program that exposes a collection of Endpoints. Each Endpoint is a portal for communicating with the world.
All the WCF communications are take place through end point. End point consists of three components.

Address

Basically URL, specifies where this WCF service is hosted .Client will use this url to connect to the service. e.g

http://localhost:8090/MyService/SimpleCalculator.svc

Binding

Binding will describes how client will communicate with service. There are different protocols available for the WCF to communicate to the Client. You can mention the protocol type based on your requirements.
A binding has several characteristics, including the following:

Transport -Defines the base protocol to be used like HTTP, Named Pipes, TCP, and MSMQ are some type of protocols.
Encoding (Optional) - Three types of encoding are available-Text, Binary, or Message Transmission Optimization Mechanism (MTOM). MTOM is an interoperable message format that allows the effective transmission of attachments or large messages (greater than 64K).
Protocol(Optional) - Defines information to be used in the binding such as Security, transaction or reliable messaging capability

The following table gives some list of protocols supported by WCF binding.

Binding	Description
BasicHttpBinding	Basic Web service communication. No security by default
WSHttpBinding	Web services with WS-* support. Supports transactions
WSDualHttpBinding	Web services with duplex contract and transaction support
WSFederationHttpBinding	Web services with federated security. Supports transactions
MsmqIntegrationBinding	Communication directly with MSMQ applications. Supports transactions
NetMsmqBinding	Communication between WCF applications by using queuing. Supports transactions
NetNamedPipeBinding	Communication between WCF applications on same computer. Supports duplex contracts and transactions
NetPeerTcpBinding	Communication between computers across peer-to-peer services. Supports duplex contracts
NetTcpBinding	Communication between WCF applications across computers. Supports duplex contracts and transactions

Contract

Collection of operation that specifies what the endpoint will communicate with outside world. Usually name of the Interface
will be mentioned in the Contract, so the client application will be aware of the operations which are exposed to the client. Each operation is a simple exchange pattern such as one-way, duplex and request/reply.
Below figure illustrate the functions of Endpoint

Example:

Endpoints will be mentioned in the web.config file on the created service.

<system.serviceModel>

<services>

      <service name="MathService"

        behaviorConfiguration="MathServiceBehavior">

       <endpoint

         address="http://localhost:8090/MyService/MathService.svc" contract="IMathService"

          binding="wsHttpBinding"/>

      </service>

    </services>

    <behaviors>

      <serviceBehaviors>

        <behavior name="MathServiceBehavior">

          <serviceMetadata httpGetEnabled="True"/>

          <serviceDebug includeExceptionDetailInFaults="true" />

        </behavior>

      </serviceBehaviors>

    </behaviors>

  </system.serviceModel>

Binding and Behavior

Binding

Simple definition for Binding describes how the client will communicate with service. We can understand with an example.
Consider a scenario say, I am creating a service that has to be used by two type of client. One of the client will access SOAP using http and other client will access Binary using TCP. How it can be done? With Web service it is very difficult to achieve, but in WCF its just we need to add extra endpoint in the configuration file.

<system.serviceModel>

    <services>

      <service name="MathService"

        behaviorConfiguration="MathServiceBehavior">

      <endpoint address="http://localhost:8090/MyService/MathService.svc"

        contract="IMathService"

          binding="wsHttpBinding"/>

<endpoint address="net.tcp://localhost:8080/MyService/MathService.svc"

contract="IMathService"

          binding="netTcpBinding"/>

      </service>

    </services>

    <behaviors>

      <serviceBehaviors>

        <behavior name="MathServiceBehavior">

          <serviceMetadata httpGetEnabled="True"/>

          <serviceDebug includeExceptionDetailInFaults="true" />

        </behavior>

      </serviceBehaviors>

    </behaviors>

  </system.serviceModel>

See how simple it is in WCF. Microsoft is making everything simple.cording to its scope: common behaviors affect all endpoints globally, service behaviors affect only service-related aspects, endpoint behaviors affect only endpoint-related properties, and operation-level behaviors affect particular operations.

Example:

In the below configuration information, I have mentioned the Behavior at Service level. In the service behavior I have mention the servieMetadata node with attribute httGetEnabled='true'. This attribute will specifies the publication of the service metadata. Similarly we can add more behavior to the service.

<system.serviceModel>

    <services>

      <service name="MathService"

        behaviorConfiguration="MathServiceBehavior">

        <endpoint address="" contract="IMathService"

          binding="wsHttpBinding"/>

      </service>

    </services>

    <behaviors>

      <serviceBehaviors>

        <behavior name="MathServiceBehavior">

          <serviceMetadata httpGetEnabled="True"/>

          <serviceDebug includeExceptionDetailInFaults="true" />

        </behavior>

      </serviceBehaviors>

    </behaviors>

  </system.serviceModel>

Contracts and Service Host

Contracts

In WCF, all services are exposed as contracts. Contract is a platform-neutral and standard way of describing what the service does. Mainly there are four types of contracts available in WCF

Service Contract

Service contracts describe the operation that service can provide. For Eg, a Service provide to know the temperature of the city based on the zip code, this service is called as Service contract. It will be created using Service and Operational Contract attribute.

Data Contract

Data contract describes the custom data type which is exposed to the client. This defines the data types, that are passed to and from service. Data types like int, string are identified by the client because it is already mention in XML schema definition language document, but custom created class or data types cannot be identified by the client e.g. Employee data type. By using DataContract we can make client to be aware of Employee data type that are returning or passing parameter to the method.

Message Contract

Default SOAP message format is provided by the WCF runtime for communication between Client and service. If it is not meeting your requirements then we can create our own message format. This can be achieved by using Message Contract attribute.

Fault Contract

Suppose the service I consumed is not working in the client application. I want to know the real cause of the problem. How I can know the error? For this we are having Fault Contract. Fault Contract provides documented view for error occurred in the service to client. This helps us to easy identity, what error has occurred.

Service Host

Service Host object is in the process of hosting the WCF service and registering endpoints. It loads the service configuration endpoints, apply the settings and start the listeners to handle the incoming request. System.ServiceModel.ServiceHost namespace hold this object. This object is created while self hosting the WCF service.
In the below example you can find that WCF service is self hosted using console application.

//Creating uri for the hosting the service

Uri uri = new Uri("http://localhost/CategoryService");

//Creating the host object for MathService

  ServiceHost host = new ServiceHost(typeof(CategoryService), uri);

//Adding endpoint to the Host object

  host.AddServiceEndpoint(typeof(ICategoryService),new WSHttpBinding(), uri);

  host.Open(); //Hosting the Service

  Console.WriteLine("Waiting for client invocations");

  Console.ReadLine();

  host.Close();

Message and Channel

Message

WCF Message is the unit of data exchange between client and service. It consists of several parts, including a body and headers.

WCF Runtime

WCF runtime is the set of object responsible for sending and receiving message. For example formatting the message, applying security and transmitting and receiving message using various protocol.

Channels:

Channels are the core abstraction for sending message to and receiving message from an Endpoint. Broadly we can categories channels as

Transport Channels

- Handles sending and receiving message from network. Protocols like HTTP, TCP name pipes and MSMQ.

Protocol Channels

- Implements SOAP based protocol by processing and possibly modifying message. e.g. WS-Security and WS-Reliability.

WCF Client and Metadata

WCF Client

WCF client is a client application creates to expose the service operations as method. Any application can host a WCF client, including an application that host a service. Therefore it is possible to create a service that includes WCF clients of other services.
A client application is a managed application that uses a WCF client to communicate with another application. To create a client application for a WCF service requires the following steps:

Get the Proxy class and service end point information

Using SvcUtil.exe we can create proxy class for the service and configuration information for endpoints. Example type the following sentence in the Visual studio command prompt, this will generate the class file and configuration file which contain information about the endpoints.

svcutil /language:vb /out:ClientCode.vb /config:app.config http://localhost:8090/MyService/SimpleCalculator.svc?wsdl

Call operations.

Add this class files in the client application. Then create the object for this class and invoke the service operation. Configuration information we got from the above step has to be added to the client application configuration file. When the client application calls the first operation, WCF automatically opens the underlying channel. This underlying channel is closed, when the object is recycled.

//Creating the proxy on client side

MyCalculatorServiceProxy.MyServiceProxy proxy

= new MyCalculatorServiceProxy.MyServiceProxy();

 Console.WriteLine("Counter: " + proxy.MyMethod());

Close the WCF client object.

After using the object created in the above steps, we have to dispose the object. Channel will be closed with the service, when the object is cleared.

Metadata

Characteristics of the service are described by the metadata. This metadata can be exposed to the client to understand the communication with service. Metadata can be set in the service by enabling the ServiceMetadata node inside the servcieBehaviour node of the service configuration file.

<system.serviceModel>

    <services>

      <service name="MathService"

        behaviorConfiguration="MathServiceBehavior">

        <endpoint address="" contract="IMathService"

          binding="wsHttpBinding"/>

      </service>

    </services>

    <behaviors>

      <serviceBehaviors>

        <behavior name="MathServiceBehavior">

    <serviceMetadata httpGetEnabled="True"/>

          <serviceDebug includeExceptionDetailInFaults="true" />

        </behavior>

      </serviceBehaviors>

    </behaviors>

  </system.serviceModel>

This metadata can be viewed while creating WCF client application using SvcUtil.exe

WCF Architecture

The following figure illustrates the major components of WCF.

Figure 1: WCF Architecture

Contracts

Contracts layer are next to that of Application layer. Developer will directly use this contract to develop the service. We are also going to do the same now. Let us see briefly what these contracts will do for us and we will also know that WCF is working on message system.

Service contracts

- Describe about the operation that service can provide. Example, Service provided to know the temperature of the city based on the zip code, this service we call as Service contract. It will be created using Service and Operational Contract attribute.

Data contract

- It describes the custom data type which is exposed to the client. This defines the data types, are passed to and from service. Data types like int, string are identified by the client because it is already mention in XML schema definition language document, but custom created class or datatype cannot be identified by the client e.g. Employee data type. By using DataContract we can make client aware that we are using Employee data type for returning or passing parameter to the method.

Message Contract

- Default SOAP message format is provided by the WCF runtime for communication between Client and service. If it is not meeting your requirements then we can create our own message format. This can be achieved by using Message Contract attribute.

Policies and Binding

- Specify conditions required to communicate with a service e.g security requirement to communicate with service, protocol and encoding used for binding.

Service Runtime

- It contains the behaviors that occur during runtime of service.

Throttling Behavior- Controls how many messages are processed.
Error Behavior - Specifies what occurs, when internal error occurs on the service.
Metadata Behavior - Tells how and whether metadata is available to outside world.
Instance Behavior - Specifies how many instance of the service has to be created while running.
Transaction Behavior - Enables the rollback of transacted operations if a failure occurs.
Dispatch Behavior - Controls how a message is processed by the WCF Infrastructure.

Messaging

- Messaging layer is composed of channels. A channel is a component that processes a message in some way, for example, by authenticating a message. A set of channels is also known as a channel stack. Channels are the core abstraction for sending message to and receiving message from an Endpoint. Broadly we can categories channels as

Transport Channels

Handles sending and receiving message from network. Protocols like HTTP, TCP, name pipes and MSMQ.

Protocol Channels

Implements SOAP based protocol by processing and possibly modifying message. E.g. WS-Security and WS-Reliability.

Activation and Hosting

- Services can be hosted or executed, so that it will be available to everyone accessing from the client. WCF service can be hosted by following mechanism

Internet information Service provides number of advantages if a Service uses Http as protocol. It does not require Host code to activate the service, it automatically activates service code.

Windows Activation Service

(WAS) is the new process activation mechanism that ships with IIS 7.0. In addition to HTTP based communication, WCF can also use WAS to provide message-based activation over other protocols, such as TCP and named pipes.

Self-Hosting

WCF service can be self hosted as console application, Win Forms or WPF application with graphical UI.

Windows Service

WCF can also be hosted as a Windows Service, so that it is under control of the Service Control Manager (SCM).

WCF Hosting

In this part of the tutorial we are going to see the four different way of hosting the WCF service. WCF service cannot exist on its own; it has to be hosted in windows process called as host process. Single host process can host multiple servers and same service type can be hosted in multiple host process. As we discussed there are mainly four different way of hosting the WCF service.

Multiple hosting and protocols supported by WCF.Microsoft has introduced the WCF concept in order to make distributed application development and deployment simple.

Hosting Environment	Supported protocol
Windows console and form application	HTTP,net.tcp,net.pipe,net.msmq
Windows service application (formerly known as NT services)	HTTP,net.tcp,net.pipe,net.msmq
Web server IIS6	http, wshttp
Web server IIS7 - Windows Process Activation Service (WAS)	HTTP,net.tcp,net.pipe,net.msmq

A summary of hosting options and supported features.

Feature	Self-Hosting	IIS Hosting	WAS Hosting
Executable Process/ App Domain	Yes	Yes	Yes
Configuration	App.config	Web.config	Web.config
Activation	Manual at startup	Message-based	Message-based
Idle-Time Management	No	Yes	Yes
Health Monitoring	No	Yes	Yes
Process Recycling	No	Yes	Yes
Management Tools	No	Yes	Yes

IIS 5/6 Hosting

The main advantage of hosting service in IIS is that, it will automatically launch the host process when it gets the first client request. It uses the features of IIS such as process recycling, idle shutdown, process health monitoring and message based activation. The main disadvantage of using IIS is that, it will support only HTTP protocol.
Let as do some hands on, to create service and host in IIS
Step 1:Start the Visual Studio 2008 and click File->New->Web Site. Select the 'WCF Service' and Location as http. This will directly host the service in IIS and click OK.

Step 2: I have created sample HelloWorld service, which will accept name as input and return with 'Hello' and name. Interface and implementation of the Service is shown below.

IMyService.cs

[ServiceContract]

public interface IMyService

    [OperationContract]

    string HelloWorld(string name);

MyService.cs

public class MyService : IMyService

    #region IMyService Members

    public string HelloWorld(string name)

        return "Hello " + name;

    #endregion

Step 3: Service file (.svc) contains name of the service and code behind file name. This file is used to know about the service.

MyService.svc

<%@ ServiceHost Language="C#" Debug="true"

Service="MyService" CodeBehind="~/App_Code/MyService.cs" %>

Step 4: Server side configurations are mentioned in the config file. Here I have mention only one end point which is configured to 'wsHttpBinding', we can also have multiple end point with differnet binding. Since we are going to hosted in IIS. We have to use only http binding. We will come to know more on endpoints and its configuration in later tutorial. Web.Config

<system.serviceModel>

  <services>

   <service behaviorConfiguration="ServiceBehavior" name="MyService">

        <endpoint address="http://localhost/IISHostedService/MyService.svc"

        binding="wsHttpBinding" contract="IMyService">

        <identity>

        <dns value="localhost"/>

        </identity>

        </endpoint>

        <endpoint address="mex" binding="mexHttpBinding" contract="IMetadataExchange"/>

   </service>

 </services>

 <behaviors>

  <serviceBehaviors>

    <behavior name="ServiceBehavior">

        <!-- To avoid disclosing metadata information,

        set the value below to false and remove the

        metadata endpoint above before deployment -->

      <serviceMetadata httpGetEnabled="true"/>

        <!-- To receive exception details in faults for

        debugging purposes, set the value below to true.

        Set to false before deployment to avoid disclosing exception information -->

        <serviceDebug includeExceptionDetailInFaults="false"/>

        </behavior>

   </serviceBehaviors>

  </behaviors>

</system.serviceModel>

Note:

You need to mention the service file name, along with the Address mention in the config file

Step 5: Now we successfully hosted the service in IIS. Next we have to consume this service in client application. Before creating the client application, we need to create the proxy for the service. This proxy is used by the client application, to interact with service. To create the proxy, run the Visual Studio 2008 command prompt. Using service utility we can create the proxy class and its configuration information.

svcutil  http://localhost/IISHostedService/MyService.svc

After executing this command we will find two file generated in the default location.

· MyService.cs - Proxy class for the WCF service

· output.config - Configuration information about the service.

Step 6: Now we will start creating the Console application using Visual Studio 2008(Client application).

Step 7: Add the reference 'System.ServiceModel'; this is the core dll for WCF.

Step 8: Create the object for the proxy class and call the HelloWorld method.

static void Main(string[] args)

            //Creating Proxy for the MyService

             MyServiceClient client = new MyServiceClient();

             Console.WriteLine("Client calling the service...");

             Console.WriteLine(client.HelloWorld("Ram"));

             Console.Read();

I hope you have enjoyed the Service hosted in IIS. Now let start the look on the self hosted service.

Self Hosting

In web service, we can host the service only in IIS, but WCF provides the user to host the service in any application (e.g. console application, Windows form etc.). Very interestingly developer is responsible for providing and managing the life cycle of the host process. Service can also be in-pro i.e. client and service in the same process. Now let's us create the WCF service which is hosted in Console application. We will also look in to creating proxy using 'ClientBase' abstract class.
Note: Host process must be running before the client calls the service, which typically means you have to prelaunch it.
Step 1: First let's start create the Service contract and it implementation. Create a console application and name it as MyCalculatorService. This is simple service which return addition of two numbers.

Step 2: Add the System.ServiceModel reference to the project.

Step 3: Create an ISimpleCalculator interface, Add ServiceContract and OperationContract attribute to the class and function as shown below. You will know more information about these contracts in later session. These contracts will expose method to outside world for using this service.

IMyCalculatorService.cs

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.ServiceModel;

namespace MyCalculatorService

    [ServiceContract()]

    public interface ISimpleCalculator

        [OperationContract()]

        int Add(int num1, int num2);

Step 4: MyCalculatorService is the implementation class for IMyCalculatorService interface as shown below.

MyCalculatorService.cs

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

namespace MyCalculatorService

    class SimpleCalculator : ISimpleCalculator

        public int Add(int num1, int num2)

            return num1 + num2;

Step 5: Now we are ready with service. Let's go for implementing the hosting process. Create a new console application and name it as 'MyCalculatorServiceHost'

Step 6: ServiceHost is the core class use to host the WCF service. It will accept implemented contract class and base address as contractor parameter. You can register multiple base addresses separated by commas, but address should not use same transport schema.

Uri httpUrl

= new Uri("http://localhost:8090/MyService/SimpleCalculator");

Uri tcpUrl

= new Uri("net.tcp://localhost:8090/MyService/SimpleCalculator");

ServiceHost host

= new ServiceHost(typeof(MyCalculatorService.SimpleCalculator), httpUrl, tcpUrl);

Multiple end points can be added to the Service using AddServiceEndpoint() method. Host.Open() will run the service, so that it can be used by any client.
Step 7: Below code show the implementation of the host process.

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.ServiceModel;

using System.ServiceModel.Description;

namespace MyCalculatorServiceHost

    class Program

        static void Main(string[] args)

            //Create a URI to serve as the base address

            Uri httpUrl = new Uri("http://localhost:8090/MyService/SimpleCalculator");

            //Create ServiceHost

            ServiceHost host

            = new ServiceHost(typeof(MyCalculatorService.SimpleCalculator), httpUrl);

            //Add a service endpoint

            host.AddServiceEndpoint(typeof(MyCalculatorService.ISimpleCalculator)

            , new WSHttpBinding(), "");

            //Enable metadata exchange

            ServiceMetadataBehavior smb = new ServiceMetadataBehavior();

            smb.HttpGetEnabled = true;

            host.Description.Behaviors.Add(smb);

            //Start the Service

            host.Open();

            Console.WriteLine("Service is host at " + DateTime.Now.ToString());

            Console.WriteLine("Host is running... Press  key to stop");

            Console.ReadLine();

Step 8: Service is hosted, now we need to implement the proxy class for the client. There are different ways of creating the proxy

Using SvcUtil.exe, we can create the proxy class and configuration file with end points.
Adding Service reference to the client application.
Implementing ClientBase class

Of these three methods, Implementing ClientBase is the best practice. If you are using rest two method, we need to create proxy class every time when we make changes in Service implementation. But this is not the case for ClientBase. It will create the proxy only at runtime and so it will take care of everything.

MyCalculatorServiceProxy.cs

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.ServiceModel;

using MyCalculatorService;

namespace MyCalculatorServiceProxy

    public class MyCalculatorServiceProxy :

        //WCF create proxy for ISimpleCalculator using ClientBase

        ClientBase,

        ISimpleCalculator

        public int Add(int num1, int num2)

            //Call base to do funtion

            return base.Channel.Add(num1, num2);

Step 9: In the client side, we can create the instance for the proxy class and call the method as shown below. Add proxy assembly as reference to the project.

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.ServiceModel;

namespace MyCalculatorServiceClient

    class Program

        static void Main(string[] args)

            MyCalculatorServiceProxy.MyCalculatorServiceProxy proxy ;

            proxy= new MyCalculatorServiceProxy.MyCalculatorServiceProxy();

            Console.WriteLine("Client is running at " + DateTime.Now.ToString());

            Console.WriteLine("Sum of two numbers... 5+5 ="+proxy.Add(5,5));

            Console.ReadLine();

Step 10 : End point (same as service) information should be added to the configuration file of the client application.

<?xml version="1.0" encoding="utf-8" ?>

<configuration>

  <system.serviceModel>

    <client>

      <endpoint address ="http://localhost:8090/MyService/SimpleCalculator"

                binding ="wsHttpBinding"

                contract ="MyCalculatorService.ISimpleCalculator">

      </endpoint>

    </client>

  </system.serviceModel>

</configuration>

Step 11: Before running the client application, you need to run the service.

This self host shows advantage such as in-Pro hosting, programmatic access and it can be used when there need singleton service. I hope you have enjoyed the Self hosting session, now let go for hosting using Windows Activation service.

Windows Activation Service

Windows Activation service is a system service available with Windows vista and windows server 2008. It is available with IIS 7.0 and it is more powerful compared to IIS 6.0 because it supports Http, TCP and named pipes were IIS 6.0 supports only Http. It can be installed and configured separately.
Hosting WCF in Activation service takes many advantages such as process recycling, isolation, idle time management and common configuration system. WAS hosted service can be created using following steps

Enable WCF for non-http protocols
Create WAS hosted service
Enable different binding to the hosted service

Enable WCF for non-http protocols

Before Start creating the service we need to configure the system to support WAS. Following are the step to configure WAS.

Click Start -> Control Panel -> programs and Features and click 'Turn Windows Components On or Off' in left pane.
Expand 'Microsoft .Net Framework 3.0' and enable "Windows Communication Foundation HTTP Activation" and "Windows Communication Foundation Non- HTTP Activation".
Next we need to add Binding to the Default Web site. As an example, we will bind the default web site to the TCP protocol. Go to the Start menu -> Programs ->Accessories. Right click on the "Command Prompt" item, and select "Run as administrator" from the context menu.
Execute the following command
C:\Windows\system32\inetsrv> appcmd.exe set site "Default Web Site" -+bindings.[protocol='net.tcp',

bindingInformation='808:*']

· That command adds the net.tcp site binding to the default web site by modifying the applicationHost.config file located in the "C:\Windows\system32\inetsrv\config" directory. Similarly we can add different protocols to the Default Web site.

Create WAS hosted service

Step 1: Next we are going to create the service, Open the Visual Studio 2008 and click New->WebSite and select WCF Service from the template and Location as HTTP .

Step 2: Create the Contract by creating interface IMathService and add ServiceContract attribute to the interface and add OperationContract attribute to the method declaration.

IMathService.cs

using System;

using System.Collections.Generic;

using System.Linq;

using System.Runtime.Serialization;

using System.ServiceModel;

using System.Text;

 [ServiceContract]

public interface IMathService

    [OperationContract]

    int Add(int num1, int num2);

    [OperationContract]

    int Subtract(int num1, int num2);

Step 3: Implementation of the IMathService interface is shown below.

MathService.cs

using System;

using System.Collections.Generic;

using System.Linq;

using System.Runtime.Serialization;

using System.ServiceModel;

using System.Text;

public class MathService : IMathService

    public int Add(int num1, int num2)

        return num1 + num2;

    public int Subtract(int num1, int num2)

        return num1 - num2;

Step 4: Service file is shown below.

MathService.svc

<%@ ServiceHost Language="C#" Debug="true" Service="MathService"

CodeBehind="~/App_Code/MathService.cs" %>

Step 5: In web.Config file, create end point with 'netTcpBinding' binding and service metadata will be published using Metadata Exchange point. So create the Metada Exchange end point with address as 'mex' and binding as 'mexTcpBinding'. Without publishing the service Metadata we cannot create the proxy using net.tcp address (e.g svcutil.exe net.tcp://localhost/WASHostedService/MathService.svc )

Web.Config

<system.serviceModel>

<services>

        <service name="MathService" behaviorConfiguration="ServiceBehavior">

        <!-- Service Endpoints -->

        <endpoint binding="netTcpBinding"

        contract="IMathService" >

        </endpoint>

               <endpoint address="mex"

               binding="mexTcpBinding" contract="IMetadataExchange"/>

               </service>

</services>

<behaviors>

<serviceBehaviors>

<behavior name="ServiceBehavior">

<!-- To avoid disclosing metadata information, set the value below

to false and remove the metadata endpoint above before deployment -->

        <serviceMetadata httpGetEnabled="true"/>

        <!-- To receive exception details in

         faults for debugging purposes, set the value below to true.

          Set to false before deployment to avoid disclosing

          exception information -->

        <serviceDebug includeExceptionDetailInFaults="false"/>

        </behavior>

</serviceBehaviors></behaviors>

</system.serviceModel>

Enable different binding to the hosted service

Go to the Start menu -> Programs ->Accessories. Right click on the "Command Prompt" item, and select "Run as administrator" from the context menu.
Execute the following command C:\Windows\system32\inetsrv>appcmd set app "Default Web Site/WASHostedServcie" /enabledProtocols:http,net.tcp

Step 6: Now the service is ready to use. Next we can create the proxy class using service uttility and add the proxy class to the client application. Creat the proxy class using Visual Studio Command prompt and execute the command

svcutil.exe net.tcp://localhost/WASHostedService/MathService.svc

Proxy and configuration file are generated in the corresponding location.

Step 6: Create the client application as shown below and add the reference 'System.ServiceModel', this is the core dll for WCF.

Step 8: Add the proxy class and configuration file to the client application. Create the object for the MathServiceClient and call the method.

Program.cs

 class Program

        static void Main(string[] args)

            MathServiceClient client = new MathServiceClient();

            Console.WriteLine("Sum of two number 5,6");

            Console.WriteLine(client.Add(5,6));

            Console.ReadLine();

So this tutorial clearly explains about the hosting the WCF in Windows Activation Service. So next we can see how to host the service using Windows Service

Windows Service Hosting

In this tutorial we are going to see the hosting WCF service in Windows service. We will use same set of code used for hosting the WCF service in Console application to this. This is same as hosting the service in IIS without message activated. There is some advantage of hosting service in Windows service.

The service will be hosted, when system starts
Process life time of the service can be controlled by Service Control Manager for windows service
All versions of Windows will support hosting WCF service.

Step 1: Now let start create the WCF service, Open the Visual Studio 2008 and click New->Project and select Class Library from the template.

Step 2: Add reference System.ServiceModel to the project. This is the core assembly used for creating the WCF service.
Step 3: Next we can create the ISimpleCalulator interface as shown below. Add the Service and Operation Contract attribute as shown below.

ISimpleCalculator.cs

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.ServiceModel;

namespace WindowsServiceHostedContract

    [ServiceContract]

    public interface ISimpleCalculator

        [OperationContract]

        int Add(int num1, int num2);

        [OperationContract]

        int Subtract(int num1, int num2);

        [OperationContract]

        int Multiply(int num1,int num2);

        [OperationContract]

        double Divide(int num1, int num2);

Step 4: Implement the ISimpleCalculator interface as shown below.

SimpleCalulator.cs

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

namespace WindowsServiceHostedService

    class SimpleCalculator

        : ISimpleCalculator

        public int Add(int num1, int num2)

            return num1+num2;

        public int Subtract(int num1, int num2)

             return num1-num2;

        public int Multiply(int num1, int num2)

             return num1*num2;

        public double Divide(int num1, int num2)

            if (num2 != 0)

                return num1 / num2;

            else

                return 0;

Step 5: Build the Project and get the dll. Now we are ready with WCF service, now we are going to see how to host the WCF Service in Windows service. Note: In this project, I have mention that we are creating both Contract and Service(implementation) are in same project. It is always good practice if you have both in different project.
Step 6: Open Visual Studio 2008 and Click New->Project and select Windows Service.

Step 7: Add the 'WindowsServiceHostedService.dll' as reference to the project. This assembly will going to act as service.
Step 8: OnStart method of the service, we can write the hosting code for WCF. We have to make sure that we are using only one service host object. On stop method you need to close the Service Host. Following code show how to host WCF service in Windows service.

WCFHostedWindowsService.cs

using System;

using System.Collections.Generic;

using System.ComponentModel;

using System.Data;

using System.Diagnostics;

using System.Linq;

using System.ServiceProcess;

using System.Text;

using System.ServiceModel;

using System.ServiceModel.Description;

namespace WCFHostedWindowsService

    partial class WCFHostedWindowsService : ServiceBase

        ServiceHost m_Host;

        public WCFHostedWindowsService()

            InitializeComponent();

        protected override void OnStart(string[] args)

            if (m_Host != null)

                m_Host.Close();

            //Create a URI to serve as the base address

            Uri httpUrl = new Uri("http://localhost:8090/MyService/SimpleCalculator");

            //Create ServiceHost

            m_Host = new ServiceHost

            (typeof(WindowsServiceHostedService.SimpleCalculator), httpUrl);

            //Add a service endpoint

            m_Host.AddServiceEndpoint

            (typeof(WindowsServiceHostedService.ISimpleCalculator), new WSHttpBinding(), "");

            //Enable metadata exchange

            ServiceMetadataBehavior smb = new ServiceMetadataBehavior();

            smb.HttpGetEnabled = true;

            m_Host.Description.Behaviors.Add(smb);

            //Start the Service

            m_Host.Open();

        protected override void OnStop()

            if (m_Host != null)

                m_Host.Close();

                m_Host = null;

        static void Main()

            ServiceBase[] ServicesToRun;

            ServicesToRun = new ServiceBase[]

                               new WCFHostedWindowsService()

};

            ServiceBase.Run(ServicesToRun);

Step 9: In order to install the service we need to have the Installer class for the Windows service. So add new Installer class to the project, which is inherited from the Installer class. Please find the below code for mentioning the Service name, StartUp type etc of the service.

ServiceInstaller.cs

using System;

using System.Collections.Generic;

using System.Text;

using System.ServiceProcess;

using System.Configuration.Install;

using System.ComponentModel;

using System.Configuration;

namespace WCFHostedWindowsService

    [RunInstaller(true)]

    public class WinServiceInstaller : Installer

        private ServiceProcessInstaller process;

        private ServiceInstaller service;

        public WinServiceInstaller()

            process = new ServiceProcessInstaller();

            process.Account = ServiceAccount.NetworkService;

            service = new ServiceInstaller();

            service.ServiceName = "WCFHostedWindowsService";

            service.DisplayName = "WCFHostedWindowsService";

            service.Description = "WCF Service Hosted";

            service.StartType = ServiceStartMode.Automatic;

            Installers.Add(process);

            Installers.Add(service);

Step 10: Build the project, we will get the WCFHostedWindowsService.exe. Next we need to install the service using Visual Studio Command Prompt. So open the command prompt by clicking Start->All Programs-> Microsoft Visual Studio 2008-> Visual Studio Tools-> Visual Studio Command Prompt Using installutil utility application.

Step 11: Now service is Hosted sucessfully and we can create the proxy class for the service and start using in the client applcaiton.

Binding

Binding will describes how client will communicate with service. There are different protocols available for the WCF to communicate to the Client. You can mention the protocol type based on your requirements.
Binding has several characteristics, including the following:

Transport

Defines the base protocol to be used like HTTP, Named Pipes, TCP, and MSMQ are some type of protocols.

Encoding (Optional)

Three types of encoding are available-Text, Binary, or Message Transmission Optimization Mechanism (MTOM). MTOM is an interoperable message format that allows the effective transmission of attachments or large messages (greater than 64K).

Protocol(Optional)

Defines information to be used in the binding such as Security, transaction or reliable messaging capability

Bindings and Channel Stacks

In WCF all the communication details are handled by channel, it is a stack of channel components that all messages pass through during runtime processing. The bottom-most component is the transport channel. This implements the given transport protocol and reads incoming messages off the wire. The transport channel uses a message encoder to read the incoming bytes into a logical Message object for further processing.

Figure 1: Bindings and Channel Stacks (draw new diagram)
After that, the message bubbles up through the rest of the channel stack, giving each protocol channel an opportunity to do its processing, until it eventually reaches the top and WCF dispatches the final message to your service implementation. Messages undergo significant transformation along the way.
It is very difficult for the developer to work directly with channel stack architecture. Because you have to be very careful while ordering the channel stack components, and whether or not they are compatible with one other.
So WCF provides easy way of achieving this using end point. In end point we will specify address, binding and contract. To know more about end point. Windows Communication Foundation follows the instructions outlined by the binding description to create each channel stack. The binding binds your service implementation to the wire through the channel stack in the middle.

Types of Binding

Let us see more detailed on predefined binding

BasicHttpBinding

It is suitable for communicating with ASP.NET Web services (ASMX)-based services that comfort with WS-Basic Profile conformant Web services.
This binding uses HTTP as the transport and text/XML as the default message encoding.
Security is disabled by default
This binding does not support WS-* functionalities like WS- Addressing, WS-Security, WS-ReliableMessaging
It is fairly weak on interoperability.

WSHttpBinding

Defines a secure, reliable, interoperable binding suitable for non-duplex service contracts.
It offers lot more functionality in the area of interoperability.
It supports WS-* functionality and distributed transactions with reliable and secure sessions using SOAP security.
It uses HTTP and HTTPS transport for communication.
Reliable sessions are disabled by default.

WSDualHttpBinding

This binding is same as that of WSHttpBinding, except it supports duplex service. Duplex service is a service which uses duplex message pattern, which allows service to communicate with client via callback.
In WSDualHttpBinding reliable sessions are enabled by default. It also supports communication via SOAP intermediaries.

WSFederationHttpBinding

This binding support federated security. It helps implementing federation which is the ability to flow and share identities across multiple enterprises or trust domains for authentication and authorization. It supports WS-Federation protocol.

NetTcpBinding

This binding provides secure and reliable binding environment for .Net to .Net cross machine communication. By default it creates communication stack using WS-ReliableMessaging protocol for reliability, TCP for message delivery and windows security for message and authentication at run time. It uses TCP protocol and provides support for security, transaction and reliability.

NetNamedPipeBinding

This binding provides secure and reliable binding environment for on-machine cross process communication. It uses NamedPipe protocol and provides full support for SOAP security, transaction and reliability. By default it creates communication stack with WS-ReliableMessaging for reliability, transport security for transfer security, named pipes for message delivery and binary encoding.

NetMsmqBinding

This binding provides secure and reliable queued communication for cross-machine environment.
Queuing is provided by using MSMQ as transport.
It enables for disconnected operations, failure isolation and load leveling

NetPeerTcpBinding

This binding provides secure binding for peer-to-peer environment and network applications.
It uses TCP protocol for communication
It provides full support for SOAP security, transaction and reliability.

Binding configuration

Binding can be configured either through configuration file or Programming. Let us see the binding representation in each method.

Administrative (Configuration file):

In the configuration file of the hosting application, you can add the element inside the element and add the properties to particular binding type. Properties corresponding to the particular binding type can be mentioned below. Name of the binding properties that you are going to use has to be mention in the end point.

<system.serviceModel>

  <services>

   <service  name="MyService">

        <endpoint address="http://localhost/IISHostedService/MyService.svc"

        binding="wsHttpBinding" bindingName="wshttpbind" contract="IMyService">

        <identity>

        <dns value="localhost"/>

        </identity>

        </endpoint>

        <endpoint address="mex" binding="mexHttpBinding" contract="IMetadataExchange"/>

    </service>

  </services>

  <bindings>

      <wsHttpBinding>

        <binding name="wshttpbind"  allowCookies="true" closeTimeout="00:01:00"

        receiveTimeout="00:01:00" />

      </wsHttpBinding>

  </bindings>

</system.serviceModel>

Programming Model:

In the following code, I have created the WSHttpBinding object and assign the properties which to be configured. This binding object is added to the Service endpoint for client communication. Similarly you can also create any type of binding and add to endpoint.

//Create a URI to serve as the base address

            Uri httpUrl = new Uri("http://localhost:8090/MyService/SimpleCalculator");

            //Create ServiceHost

            ServiceHost host =

             new ServiceHost(typeof(MyCalculatorService.SimpleCalculator), httpUrl);

            //Create Binding to add to end point

            WSHttpBinding wshttpbind = new WSHttpBinding();

            wshttpbind.AllowCookies = true;

            wshttpbind.CloseTimeout = new TimeSpan(0, 1, 0);

            wshttpbind.ReceiveTimeout  = new TimeSpan(0, 1, 0);

            //Add a service endpoint

            host.AddServiceEndpoint

            (typeof(MyCalculatorService.ISimpleCalculator), wshttpbind, "");

            //Enable metadata exchange

            ServiceMetadataBehavior smb = new ServiceMetadataBehavior();

            smb.HttpGetEnabled = true;

            host.Description.Behaviors.Add(smb);

            //Start the Service

            host.Open();

            Console.WriteLine("Service is host at " + DateTime.Now.ToString());

            Console.WriteLine("Host is running... Press  key to stop");

            Console.ReadLine();

Note: It is always good if you configure the binding properties using configuration file, because while moving to the production you no need to change in the code and recompile it. It is always good practice to represent in the configuration file.

Metadata Exchange

WCF provides rich infrastructure for Exporting, Publishing, retrieving and Importing the metadata. WCF uses the Metadata to describe how to interact with the service endpoint. Using the metadata, client will create the proxy class for the service using SvcUtil.exe

Exporting Service Metadata

It is the process of describing the service endpoint so that client can understand how to use the service.

Publishing Service Metadata

It is the process publishing metadata. It involves converting CLR type and binding information into WSDL or some other low level representation.

Retrieving Service Metadata

It is the process of retrieving the metadata. It uses WS-MetadataExcahge or HTTP protocol for retrieving the metadata. Importing Service Metadata - It is the process of generating the abstract representation of the service using metadata.
Now we are going to focus mainly on publishing metadata. There are two way to publish metadata, either we can use HTTP-GET or through message exchange endpoint. By default service metadata is turn-off due to security reason. WCF metadata infrastructure resides in System.ServiceModel.Description namespace. Service metadata can be used for following purpose

Automatically generating the client for consuming service
Implementing the service description
Updating the binding for a client

Now let us understand the publishing the metadata using HTTP-GET method.

HTTP_GET Enabled Metadata

We will use ServiceBehaviour to publish the metadata using HTTP-GET. This can be configures either administratively or Programmatically. Http and Https can expose by appending "?wsdl" to the end of the service address. For example service address is http://localhost:9090/MyCalulatorService , HTTP-Get metadata address is given by http://localhost:9090/MyCalulatorService?wsdl.

Administrative (Configuration file):

In the below mention configuration information, you can find the behavior section in the ServiceBehavior. You can expose the metadata using ServiceMetadata node with httpGetEnable='True'.

<system.serviceModel>

   <services>

        <service behaviorConfiguration="ServiceBehavior" name="MyService">

           <endpoint address="http://localhost/IISHostedService/MyService.svc"

            binding="wsHttpBinding" contract="IMyService">

               <identity>

               <dns value="localhost"/>

               </identity>

            </endpoint>

        </service>

  </services>

  <behaviors>

    <serviceBehaviors>

        <behavior name="ServiceBehavior">

                <!-Setting httpGetEnabled you can publish the metadata -->

               <serviceMetadata httpGetEnabled="true"/>

               </behavior>

            </serviceBehaviors>

   </behaviors>

</system.serviceModel>

Progarmming Model:

Using ServiceMetadataBehavior you can enable the metadata exchange. In the following code, I have created the ServiceMetadataBehavior object and assigned HttpGetEnabled property to true. Then you have to add the behavior to host description as shown. This set of code will publish the metadata using HTTP-GET.

 //Create a URI to serve as the base address

            Uri httpUrl = new Uri("http://localhost:8090/MyService/SimpleCalculator");

            //Create ServiceHost

            ServiceHost host = new

            ServiceHost(typeof(MyCalculatorService.SimpleCalculator), httpUrl);

            //Add a service endpoint

            host.AddServiceEndpoint

            (typeof(MyCalculatorService.ISimpleCalculator), new WSHttpBinding(), "");

            //Enable metadata exchange

            ServiceMetadataBehavior smb = new ServiceMetadataBehavior();

            //Enable metadata exchange using HTTP-GET

            smb.HttpGetEnabled = true;

            host.Description.Behaviors.Add(smb);

            //Start the Service

            host.Open();

            Console.WriteLine("Service is host at " + DateTime.Now.ToString());

            Console.WriteLine("Host is running... Press  key to stop");

            Console.ReadLine();

Metadata Exchange Endpoint

Exposing the metadata using HTTP-GET has a disadvantage, such that there is no guarantee that other platforms you interact will support it. There is other way of exposing the using special endpoint is called as Metadata Exchange Endpoint. You can have as many metadata exchange endpoints as you want.

Address

It is basically Uri to identify the metadata. You can specify as address in the endpoint but append with "mex" keyword. For example "http://localhost:9090/MyCalulatorService/mex"

Binding

There are four types of bindings supported for metadata exchange. They are mexHttpBinding, mexHttpsBinding, mexNamedPipesBinding, mexTcpBinding.

Contract

IMetadataExchange is the contract used for MEX endpoint. WCF service host automatically provides the implementation for this IMetadataExcahnge while hosting the service.
You can create the Metadata Exchange Endpoint either Administrative (configuration file) or programmatically.

Administrative (Configuration file):

In the configuration file of the hosting application, you can add metadata exchange endpoint as shown below.

<system.serviceModel>

<services>

        <service name="MyService">

        <endpoint address="http://localhost/IISHostedService/MyService.svc"

        binding="wsHttpBinding" contract="IMyService">

        <identity>

        <dns value="localhost"/>

        </identity>

        </endpoint>

        <endpoint address="mex" binding="mexHttpBinding" contract="IMetadataExchange"/>

        </service>

</services>

</system.serviceModel>

Programming Model:

In the following code I have mention about creating the Metadata Exchange Endpoint through coding. Steps to create the metadata endpoint are

Create the ServiceMetadataBehavior object and add to Service host description.

ServiceMetadataBehavior smb = new ServiceMetadataBehavior();

            host.Description.Behaviors.Add(smb);

Create the metadata binding object using MetadataExchangeBinding

Binding mexBinding = MetadataExchangeBindings.CreateMexHttpBinding ();

3. Add the endpoint to the service host with address, binding and contract.

host.AddServiceEndpoint(typeof(IMetadataExchange), mexBinding, "mex");

Complete code for hosting the service with metadata exchange endpoint is shown below.

//Create a URI to serve as the base address

            Uri httpUrl = new Uri("http://localhost:8090/MyService/SimpleCalculator");

            //Create ServiceHost

            ServiceHost host = new

            ServiceHost(typeof(MyCalculatorService.SimpleCalculator), httpUrl);

            //Add a service endpoint

            host.AddServiceEndpoint

            (typeof(MyCalculatorService.ISimpleCalculator), new WSHttpBinding(), "");

            //Enable metadata exchange

            ServiceMetadataBehavior smb = new ServiceMetadataBehavior();

            host.Description.Behaviors.Add(smb);

            Binding mexBinding = MetadataExchangeBindings.CreateMexHttpBinding ();

            //Adding metadata exchange endpoint

            host.AddServiceEndpoint(typeof(IMetadataExchange), mexBinding, "mex");

            //Start the Service

            host.Open();

            Console.WriteLine("Service is host at " + DateTime.Now.ToString());

            Console.WriteLine("Host is running... Press  key to stop");

            Console.ReadLine();

Contracts

Windows Communication Foundation (WCF, formerly known as Indigo) is built upon the foundation of web services messaging and related standards, while at the same time makes it possible to serialize messages in a more compact binary format, or in a more proprietary way. Still, the core message can always be represented in XML, therefore be considered compatible with any platform that understands XML, and agrees on the contract that defines said messaging between systems.
The contract is a platform-neutral and standard way of describing what the service does. WCF defines four types of contracts:

Service Contract

Service contract describes the operation that service provide. A Service can have more than one service contract but it should have at least one Service contract.
Service Contract can be define using [ServiceContract] and [OperationContract] attribute. [ServiceContract] attribute is similar to the [WebServcie] attribute in the WebService and [OpeartionContract] is similar to the [WebMethod] in WebService.

It describes the client-callable operations (functions) exposed by the service
It maps the interface and methods of your service to a platform-independent description
It describes message exchange patterns that the service can have with another party. Some service operations might be one-way; others might require a request-reply pattern
It is analogous to the element in WSDL

To create a service contract you define an interface with related methods representative of a collection of service operations, and then decorate the interface with the ServiceContract Attribute to indicate it is a service contract. Methods in the interface that should be included in the service contract are decorated with the OperationContract Attribute.

[ServiceContract()]

    public interface ISimpleCalculator

        [OperationContract()]

        int Add(int num1, int num2);

Once we define Service contract in the interface, we can create implement class for this interface.

public  class SimpleCalculator : ISimpleCalculator

        public int Add(int num1, int num2)

            return num1 + num2;

With out creating the interface, we can also directly created the service by placing Contract in the implemented class. But it is not good practice of creating the service

[ServiceContract()]

   public class SimpleCalculator

       [OperationContract()]

       public int Add(int num1, int num2)

           return num1 + num2;

Now you have some fundamental idea on Service contract. Next we will look into Data Contract.

Data Contract

A data contract is a formal agreement between a service and a client that abstractly describes the data to be exchanged.
Data contract can be explicit or implicit. Simple type such as int, string etc has an implicit data contract. User defined object are explicit or Complex type, for which you have to define a Data contract using [DataContract] and [DataMember] attribute.
A data contract can be defined as follows:

It describes the external format of data passed to and from service operations
It defines the structure and types of data exchanged in service messages
It maps a CLR type to an XML Schema
t defines how data types are serialized and deserialized. Through serialization, you convert an object into a sequence of bytes that can be transmitted over a network. Through deserialization, you reassemble an object from a sequence of bytes that you receive from a calling application.
It is a versioning system that allows you to manage changes to structured data

We need to include System.Runtime.Serialization reference to the project. This assembly holds the DataContract and DataMember attribute.
Create user defined data type called Employee. This data type should be identified for serialization and deserialization by mentioning with [DataContract] and [DataMember] attribute.

 [ServiceContract]

    public interface IEmployeeService

        [OperationContract]

        Employee GetEmployeeDetails(int EmpId);

    [DataContract]

    public class Employee

        private string m_Name;

        private int m_Age;

        private int m_Salary;

        private string m_Designation;

        private string m_Manager;

        [DataMember]

        public string Name

            get { return m_Name; }

            set { m_Name = value; }

        [DataMember]

        public int Age

            get { return m_Age; }

            set { m_Age = value; }

        [DataMember]

        public int Salary

            get { return m_Salary; }

            set { m_Salary = value; }

        [DataMember]

        public string Designation

            get { return m_Designation; }

            set { m_Designation = value; }

        [DataMember]

        public string Manager

            get { return m_Manager; }

            set { m_Manager = value; }

Implementation of the service class is shown below. In GetEmployee method we have created the Employee instance and return to the client. Since we have created the data contract for the Employee class, client will aware of this instance whenever he creates proxy for the service.

public class EmployeeService : IEmployeeService

        public Employee GetEmployeeDetails(int empId)

            Employee empDetail = new Employee();

            //Do something to get employee details and assign to 'empDetail' properties

            return empDetail;

Client side

On client side we can create the proxy for the service and make use of it. The client side code is shown below.

protected void btnGetDetails_Click(object sender, EventArgs e)

            EmployeeServiceClient objEmployeeClient = new EmployeeServiceClient();

            Employee empDetails;

            empDetails = objEmployeeClient.GetEmployeeDetails(empId);

//Do something on employee details

Message Contract

Message

Message is the packet of data which contains important information. WCF uses these messages to transfer information from Source to destination.
WCF uses SOAP(Simple Object Access Protocol) Message format for communication. SOAP message contain Envelope, Header and Body.SOAP envelope contails name, namespace,header and body element. SOAP Hear contain important information which are not directly related to message. SOAP body contains information which is used by the target.

Diagram Soap envelope

Message Pattern

It describes how the programs will exchange message each other. There are three way of communication between source and destination

Simplex - It is one way communication. Source will send message to target, but target will not respond to the message.
Request/Replay - It is two way communications, when source send message to the target, it will resend response message to the source. But at a time only one can send a message
Duplex - It is two way communication, both source and target can send and receive message simultaniouly.

What is Message contract?

As I said earlier, WCF uses SOAP message for communication. Most of the time developer will concentrate more on developing the DataContract, Serializing the data, etc. WCF will automatically take care of message. On Some critical issue, developer will also require control over the SOAP message format. In that case WCF provides Message Contract to customize the message as per requirement.
WCF supports either RPC(Remote Procedure Call) or Message style operation model. In the RPC model, you can develop operation with Ref and out parameter. WCF will automatically create the message for operation at run time. In Message style operation WCF allows to customize the message header and define the security for header and body of the message.

Defining Message Contract

Message contract can be applied to type using MessageContract attribute. Custom Header and Body can be included to message using 'MessageHeader' and 'MessageBodyMember'atttribute. Let us see the sample message contract definition.

[MessageContract]

public class EmployeeDetails

    [MessageHeader]

    public string EmpID;

    [MessageBodyMember]

    public string Name;

    [MessageBodyMember]

    public string Designation;

    [MessageBodyMember]

    public int Salary;

    [MessageBodyMember]

    public string Location;

When I use this EmployeeDeatils type in the service operation as parameter. WCF will add extra header call 'EmpID' to the SOAP envelope. It also add Name, Designation, Salary, Location as extra member to the SOAP Body.

Rules :

You have to follow certain rules while working with Message contract

When using Message contract type as parameter, Only one parameter can be used in servicie Operation

2.           [OperationContract]

3.           void SaveEmployeeDetails(EmployeeDetails emp);

Service operation either should return Messagecontract type or it should not return any value

5.           [OperationContract]

6.           EmployeeDetails GetEmployeeDetails();

Service operation will accept and return only message contract type. Other data types are not allowed.

8.           [OperationContract]

9.           EmployeeDetails ModifyEmployeeDetails(EmployeeDetails emp);

Note: If a type has both Message and Data contract, service operation will accept only message contract.

MessageHeaderArray Attribute

Consider the Message contract type definition as shown below.

[MessageContract]

    public class Department

        [MessageHeader]

        public string DepartmentID;

        [MessageHeader]

        public string DepartmentName;

        [MessageHeader]

        public Employees Employee();

In this we are having array of Employee type as message header. When this converted to SOAP Header it looks as shown below.

<Department>

  <DepartmentID>PRO1243</DepartmentID>

  <DepartmentName>Production</DepartmentName>

  <Employees>

    <Employee>Sam</Employee>

    <Employee>Ram</Employee>

    <Employee>Raja</Employee>

  </Employees>

</Department>

Suppose you want to show the all employee detail in same level. We can use MessageHeaderArray attribute which will serialize the array element independently. If you use the MessageHeaderArray attribute of Employees, SOAP message will look as shown below.

<Department>

  <DepartmentID>PRO1243</DepartmentID>

  <DepartmentName>Production</DepartmentName>

  <Employee>Sam</Employee>

  <Employee>Ram</Employee>

  <Employee>Raja</Employee>

</Department>

Note: MessageHeaderArray Attribute is applicable only for Array, not for collection.

Message Contract Properties

ProtectionLevel

You can mention the MessageHeader or MessageBodyMember to be signed or Encrypted using ProtectionLevel property.

Example

using System.Net.Security;

    [MessageContract]

    public class EmployeeDetails

        [MessageHeader(ProtectionLevel=ProtectionLevel.None)]

        public string EmpID;

        [MessageBodyMember(ProtectionLevel = ProtectionLevel.Sign )]

        public string Name;

        [MessageBodyMember(ProtectionLevel = ProtectionLevel.Sign )]

        public string Designation;

        [MessageBodyMember(ProtectionLevel=ProtectionLevel.EncryptAndSign)]

        public int Salary;

In the above type definition, we have made the different protection level for body. But the protection level of the body is determind by the highest ProtectionLevel property. By default if you are not specifying the protection level it takes 'EncryptAndSign'. So it good if you specify minimum ProtectionLevel required.

Name and Namespace:

SOAP representation of the message element can be change by mentioning Name and Namespace property of the Header and Body member. By default namespace is the same as the namespace of the service contract that the message is participating. In the below example, I have mention the Name property to the EmpID and Name.

[MessageContract]

    public class EmployeeDetails

        [MessageHeader(Name="ID")]

        public string EmpID;

        [MessageBodyMember(Name="EmployeeName")]

        public string Name;

        [MessageBodyMember()]

        public string Designation;

        [MessageBodyMember()]

        public int Salary;

When SOAP message representation, its name is changed to ID and EmployeeName.

<EmployeeDetails>

  <ID>45634</ID>

  <EmployeeName>Sam</EmployeeName>

  <Designation>Software Engineer</Designation>

  <Salary>25000</Salary>

</EmployeeDetails>

Order

The order of the body elements are alpehabetical by default. But you can control the order, usiing Order property in the MessageBody attribute.

[MessageContract]

    public class EmployeeDetails

        [MessageHeader()]

        public string EmpID;

        [MessageBodyMember(Order=2)]

        public string Name;

        [MessageBodyMember(Order=3)]

        public string Designation;

        [MessageBodyMember(Order=1)]

        public int Salary;

Fault Contract

Service that we develop might get error in come case. This error should be reported to the client in proper manner. Basically when we develop managed application or service, we will handle the exception using try- catch block. But these exceptions handlings are technology specific.
In order to support interoperability and client will also be interested only, what wents wrong? not on how and where cause the error.
By default when we throw any exception from service, it will not reach the client side. WCF provides the option to handle and convey the error message to client from service using SOAP Fault contract.
Suppose the service I consumed is not working in the client application. I want to know the real cause of the problem. How I can know the error? For this we are having Fault Contract. Fault Contract provides documented view for error accorded in the service to client. This help as to easy identity the what error has accord. Let us try to understand the concept using sample example.
Step 1: I have created simple calculator service with Add operation which will throw general exception as shown below

//Service interface

[ServiceContract()]

    public interface ISimpleCalculator

        [OperationContract()]

        int Add(int num1, int num2);

//Service implementation

public  class SimpleCalculator : ISimpleCalculator

        public int Add(int num1, int num2)

            //Do something

            throw new Exception("Error while adding number");

Step 2: On client side code. Exceptions are handled using try-Catch block. Even though I have capture the exception when I run the application. I got the message that exceptions are not handled properly.

try

      MyCalculatorServiceProxy.MyCalculatorServiceProxy proxy

       = new MyCalculatorServiceProxy.MyCalculatorServiceProxy();

      Console.WriteLine("Client is running at " + DateTime.Now.ToString());

      Console.WriteLine("Sum of two numbers... 5+5 =" + proxy.Add(5, 5));

      Console.ReadLine();

   catch (Exception ex)

      Console.WriteLine(ex.Message);

      Console.ReadLine();

Step 3: Now if you want to send exception information form service to client, you have to use FaultException as shown below.

        public int Add(int num1, int num2)

            //Do something

            throw new FaultException("Error while adding number");

Step 4: You can also create your own Custom type and send the error information to the client using FaultContract. These are the steps to be followed to create the fault contract.

Define a type using the data contract and specify the fields you want to return.
Decorate the service operation with the FaultContract attribute and specify the type name.
Raise the exception from the service by creating an instance and assigning properties of the custom exception.

Step 6: Defining the type using Data Contract

    [DataContract()]

    public class CustomException

        [DataMember()]

        public string Title;

        [DataMember()]

        public string ExceptionMessage;

        [DataMember()]

        public string InnerException;

        [DataMember()]

        public string StackTrace;

Step 7: Decorate the service operation with the FaultContract

    [ServiceContract()]

    public interface ISimpleCalculator

        [OperationContract()]

        [FaultContract(typeof(CustomException))]

        int Add(int num1, int num2);

Step 8: Raise the exception from the service

        public int Add(int num1, int num2)

            //Do something

            CustomException ex = new CustomException();

            ex.Title = "Error Funtion:Add()";

            ex.ExceptionMessage = "Error occur while doing add function.";

            ex.InnerException = "Inner exception message from serice";

            ex.StackTrace = "Stack Trace message from service.";

            throw new FaultException(ex,"Reason: Testing the Fault contract") ;

Step 9: On client side, you can capture the service exception and process the information, as shown below.

try

      MyCalculatorServiceProxy.MyCalculatorServiceProxy proxy

      = new MyCalculatorServiceProxy.MyCalculatorServiceProxy();

       Console.WriteLine("Client is running at " + DateTime.Now.ToString());

       Console.WriteLine("Sum of two numbers... 5+5 =" + proxy.Add(5, 5));

       Console.ReadLine();

    catch (FaultException ex)

        //Process the Exception

Instance Management

Instance management refers to the way a service handles a request from a client. Instance management is set of techniques WCF uses to bind client request to service instance, governing which service instance handles which client request. It is necessary because application will differ in their need for scalability, performance, durability, transaction and queued calls.
Basically there are three instance modes in WCF:

Configuration:

Instance mode can be configured using ServiceBehavior attribute. This can be specified at implementing the service contract as shown below.

 [ServiceContract()]

    public interface IMyService

        [OperationContract]

        int MyMethod();

    [ServiceBehavior(InstanceContextMode=InstanceContextMode.Single)]

    public class MyService:IMyService

        public int MyMethod()

            //Do something

Per-Call Service

When WCF service is configured for Per-Call instance mode, Service instance will be created for each client request. This Service instance will be disposed after response is sent back to client.

Following diagram represent the process of handling the request from client using Per-Call instance mode.

Let as understand the per-call instance mode using example.
Step 1: Create the service contract called IMyService and implement the interface. Add service behavior attribute to the service class and set the InstanceContextMode property to PerCall as show below.

    [ServiceContract()]

    public interface IMyService

        [OperationContract]

        int MyMethod();

Step 2: In this implementation of MyMethod operation, increment the static variable(m_Counter). Each time while making call to the service, m_Counter variable is incremented and return the value to the client.

    [ServiceBehavior(InstanceContextMode=InstanceContextMode.PerCall)]

    public class MyService:IMyService

        static int m_Counter = 0;

        public int MyMethod()

            m_Counter++;

            return m_Counter;

Step 3: Client side, create the proxy for the service and call "myMethod" operation multiple time.

        static void Main(string[] args)

            Console.WriteLine("Service Instance mode: Per-Call");

            Console.WriteLine("Client  making call to service...");

            //Creating the proxy on client side

            MyCalculatorServiceProxy.MyServiceProxy proxy =

             new MyCalculatorServiceProxy.MyServiceProxy();

            Console.WriteLine("Counter: " + proxy.MyMethod());

            Console.WriteLine("Counter: " + proxy.MyMethod());

            Console.WriteLine("Counter: " + proxy.MyMethod());

            Console.WriteLine("Counter: " + proxy.MyMethod());

            Console.ReadLine();

Surprisingly, all requests to service return '1', because we configured the Instance mode to Per-Call. Service instance will created for each request and value of static variable will be set to one. While return back, service instance will be disposed.

Per-Session Service

When WCF service is configured for Per-Session instance mode, logical session between client and service will be maintained. When the client creates new proxy to particular service instance, a dedicated service instance will be provided to the client. It is independent of all other instance.

Let as understand the Per-Session instance mode using example.
Step 1: Create the service contract called IMyService and implement the interface. Add service behavior attribute to the service class and set the InstanceContextMode property to PerSession as show below.

    [ServiceContract()]

    public interface IMyService

        [OperationContract]

        int MyMethod();

Step 2: In this implementation of MyMethod operation, increment the static variable (m_Counter). Each time while making call to the service, m_Counter variable will be incremented and return the value to the client.

    [ServiceBehavior(InstanceContextMode=InstanceContextMode.PerSession)]

    public class MyService:IMyService

        static int m_Counter = 0;

        public int MyMethod()

            m_Counter++;

            return m_Counter;

Step 3: Client side, create the proxy for the service and call "myMethod" operation multiple time.

        static void Main(string[] args)

            Console.WriteLine("Service Instance mode: Per-Session");

            Console.WriteLine("Client  making call to service...");

            //Creating the proxy on client side

            MyCalculatorServiceProxy.MyServiceProxy proxy =

            new MyCalculatorServiceProxy.MyServiceProxy();

            Console.WriteLine("Counter: " + proxy.MyMethod());

            Console.WriteLine("Counter: " + proxy.MyMethod());

            Console.WriteLine("Counter: " + proxy.MyMethod());

            Console.WriteLine("Counter: " + proxy.MyMethod());

            Console.ReadLine();

All request to service return incremented value (1, 2, 3, 4), because we configured the instance mode to Per-Session. Service instance will be created once the proxy is created at client side. So each time request is made to the service, static variable is incremented. So each call to MyMethod return incremented value.

Singleton Service

When WCF service is configured for Singleton instance mode, all clients are independently connected to the same single instance. This singleton instance will be created when service is hosted and, it is disposed when host shuts down.
.

Let as understand the Singleton Instance mode using example.
Step 1: Create the service contract called IMyService and implement the interface. Add service behavior attribute to the service class and set the InstanceContextMode property to Single as show below.

    [ServiceContract()]

    public interface IMyService

        [OperationContract]

        int MyMethod();

    [ServiceBehavior(InstanceContextMode=InstanceContextMode.Single)]

    public class MyService:IMyService

        static int m_Counter = 0;

        public int MyMethod()

            m_Counter++;

            return m_Counter;

Step 3: Client side, create the two proxies for the service and made a multiple call to MyMethod.

static void Main(string[] args)

Console.WriteLine("Service Instance mode: Singleton");

            Console.WriteLine("Client 1 making call to service...");

            //Creating the proxy on client side

            MyCalculatorServiceProxy.MyServiceProxy proxy =

            new MyCalculatorServiceProxy.MyServiceProxy();

            Console.WriteLine("Counter: " + proxy.MyMethod());

            Console.WriteLine("Counter: " + proxy.MyMethod());

            Console.WriteLine("Counter: " + proxy.MyMethod());

            Console.WriteLine("Client 2 making call to service...");

            //Creating new proxy to act as new client

            MyCalculatorServiceProxy.MyServiceProxy proxy2 =

             new MyCalculatorServiceProxy.MyServiceProxy();

            Console.WriteLine("Counter: " + proxy2.MyMethod());

            Console.WriteLine("Counter: " + proxy2.MyMethod());

            Console.ReadLine();

When two proxy class made a request to service, single instance at service will handle it and it return incremented value (1, 2, 3, 4), because instance mode is configured to 'Single'. Service instance is created when it is hosted. So this instance will remain till host is shutdown.

Instance Deactivation

In Instance Management System tutorial, you learn how to create sessionful service instance. Basically service instance is hosted in a context. Session actually correlated the client message not to the instance, but to the context that host it. When session starts, context is created and when it closes, context is terminated. WCF provides the option of separating the two lifetimes and deactivating the instance separately from its context.
ReleaseInstanceMode property of the OberationalBehavior attribute used to control the instance in relation to the method call.
Followings are the list Release mode available in the ReleaseInstanceMode

RealeaseInstanceMode.None
RealeaseInstanceMode.BeforeCall
RealeaseInstanceMode.AfterCall
RealeaseInstanceMode.BeforeAndAfterCall

Below code show, how to add the 'ReleaseInstanceMode' property to the operational behavior.

    [ServiceContract()]

    public interface ISimpleCalculator

        [OperationContract()]

        int Add(int num1, int num2);

   [OperationBehavior(ReleaseInstanceMode=ReleaseInstanceMode.BeforeCall]

    public int Add(int num1, int num2)

        return num1 + num2;

ReleaseInstanceMode.None

This property means that it will not affect the instance lifetime. By default ReleaseInstanceMode property is set to 'None'.

ReleaseInstanceMode.BeforeCall

This property means that it will create new instance before a call is made to the operation.
If the instance is already exist,WCF deactivates the instance and calls Dispose() before the call is done. This is designed to optimize a method such as Create()

ReleaseInstanceMode.AfterCall

This property means that it will deactivate the instance after call is made to the method.
This is designed to optimize a method such a Cleanup()

ReleaseInstanceMode.BeforeAndAfterCall

This is means that it will create new instance of object before a call and deactivates the instance after call. This has combined effect of using ReleaseInstanceMode.BeforeCall and ReleaseInstanceMode.AfterCall

Explicit Deactivate

You can also explicitly deactivate instance using InstanceContext object as shown below.

   [ServiceContract()]

    public interface IMyService

        [OperationContract]

        void MyMethod();

    [ServiceBehavior(InstanceContextMode=InstanceContextMode.Single)]

    public class MyService:IMyService

        public void MyMethod()

           //Do something

           OperationContext.Current.InstanceContext.ReleaseServiceInstance();

Durable Service

Durable services are WCF services that persist service state information even after service host is restarted or Client. It means that durable services have the capability to restore their own state when they are recycled. It can use data store like SQL database for maintain instance state. It is new feature in .Net 3.5
You might think that we can also maintain session using WCF sessions, but content in the session environment is not persisted by default. If the service is shut down or client closes the proxy, data will be lost. But in case of Durable service it is still maintained.

Working:

When Durable service is created with database as data store, it will maintain all its state information in the table.
When a client make a request to the service, instance of the service is serialized, a new GUID is generated. This serialized instance xml and key will be saved in the database. We will call this GUID as instanceID. Service will send the instanceID to the client, so later it can use this id to get the instance state back. Even when client is shut down, instanceId will be saved at the client side. So when ever client opening the proxy, it can get back the previous state.

Defining the Durable Service

Durable service can be implemented using [DurableService()] attribute. It takes 'CanCreateInstance' and 'CompletesInstance' property to mention on which operation instance state has to be saved and destroyed.

CanCreateInstance = true: Calling this operation results in creating the serialization and inserting it into the datastore.
CompletesInstance = true: Calling this operation results in deleting the persisted instance from the datastore.

    [Serializable]

    [DurableService()]

    public class MyService :IMyservice

        [DurableOperation(CanCreateInstance = true)]

        public int StartPersistance()

            //Do Something

     [DurableOperation(CompletesInstance = true)]

        public void EndPersistence()

            //Do Something

How to Create Durable Service

Let us understand more about the durable service by creating Simple Calculator service which persist the instance state in SQL server database.
Step 1: Start the Visual Studio 2008 and click File->New->Web Site. Select the 'WCF Service'

Step 2: Create interface and decorate with Service and Operation contract.

    [ServiceContract()]

    public interface ISimpleCalculator

        [OperationContract]

        int Add(int num);

        [OperationContract]

        int Subtract(int num);

        [OperationContract]

        int Multiply(int num);

        [OperationContract]

        void EndPersistence();

Step 3: You need to add [Serializable] And [DurableService()] attribute to the service implementation. Set CanCreateInstance = true property to the operation in which instance state has to be persisted and set CompletesInstance = true when state has to be destroyed. In this implementation, we are going to persist the 'currentValue' variable value to the database.

using System.Runtime.Serialization;

using System.ServiceModel;

using System.Text;

using System.ServiceModel.Description;

    [Serializable]

    [DurableService()]

    public class SimpleCalculator :ISimpleCalculator

        int currentValue = default(int);

        [DurableOperation(CanCreateInstance = true)]

        public int Add(int num)

            return (currentValue += num);

        [DurableOperation()]

        public int Subtract(int num)

            return (currentValue -= num);

        [DurableOperation()]

        public int Multiply(int num)

            return (currentValue *= num);

        [DurableOperation(CompletesInstance = true)]

        public void EndPersistence()

Step 4: Before configuring the database information in the durable service, you need to set up DataStore environment. Microsoft provides inbuilt sqlPersistance provider. To set up the database environment, run the these sql query located at following location 'C:\Windows\Microsoft.NET\Framework\v3.5\SQL\EN'

SqlPersistenceProviderSchema.sql
SqlPersistenceProviderLogic.sql

Step 5: In order to support durable service, you need to use Context binding type. tag is used to configure the persistence provider.

<system.serviceModel>

        <services>

               <service name="SimpleCalculator" behaviorConfiguration="ServiceBehavior">

               <!-- Service Endpoints -->

               <endpoint address="" binding="wsHttpContextBinding"

               bindingConfiguration="browConfig" contract="ISimpleCalculator">

               <identity>

               <dns value="localhost"/>

               </identity>

               </endpoint>

               <endpoint address="mex" binding="mexHttpBinding"

               contract="IMetadataExchange"/>

               </service>

        </services>

        <behaviors>

               <serviceBehaviors>

               <behavior name="ServiceBehavior">

               <serviceMetadata httpGetEnabled="true"/>

        <serviceDebug includeExceptionDetailInFaults="true"/>

    <persistenceProvider

     type="System.ServiceModel.Persistence.SqlPersistenceProviderFactory,

         System.WorkflowServices, Version=3.5.0.0, Culture=neutral,

          PublicKeyToken=31bf3856ad364e35" connectionStringName="DurableServiceStore"

                               persistenceOperationTimeout="00:00:10"

                               lockTimeout="00:01:00"

                               serializeAsText="true"/>

                       </behavior>

                       </serviceBehaviors>

               </behaviors>

    <bindings>

      <wsHttpContextBinding >

        <binding name="browConfig" >

          <security mode="None"></security>

        </binding>

      </wsHttpContextBinding>

    </bindings>

</system.serviceModel>

<connectionStrings>

<add name="DurableServiceStore"

connectionString="Data Source=saravanakumar;Initial Catalog

=DurableServiceStore;Integrated Security=True"/>

</connectionStrings>

Step 6: Create the console client application and name it as DurableServiceClient

Step 7: Add following reference to client application

System.ServiceModel
System.WorkflowService

Step 8: Add WCF service as Service Reference to the project and name it as SimpleCalculatorService

Step 9: Create the Helper class called it as Helper.cs. This helper class is used to Store, Retrieve and set the context at the client side. Context information will be saved in 'token_context.bin' file. Copy and paste the below code to your helper file.

Helper.cs

using System.ServiceModel.Channels;

using System.ServiceModel;

using System.Net;

using System.IO;

using System.Runtime.Serialization.Formatters.Binary;

    public class Helper

        static readonly String TokenContextFileName = "token_context.bin";

        public static IDictionary LoadContext()

            IDictionary ctx = null;

try

                using (FileStream fs = new

                FileStream(TokenContextFileName, FileMode.Open, FileAccess.Read))

                    BinaryFormatter bf = new BinaryFormatter();

                    ctx = bf.Deserialize(fs) as IDictionary;

                    fs.Close();

            catch (Exception ex)

            return ctx;

        public static void SaveContext(IClientChannel channel)

            IDictionary ctx = null;

            IContextManager cm = channel.GetProperty();

            if (cm != null)

                ctx = cm.GetContext() as IDictionary;

try

                    using (FileStream fs

                    = new FileStream(TokenContextFileName, FileMode.CreateNew))

                        BinaryFormatter bf = new BinaryFormatter();

                        bf.Serialize(fs, ctx);

                        fs.Close();

                catch (Exception ex)

        public static void DeleteContext()

try

                File.Delete(TokenContextFileName);

            catch (Exception ex)

        public static void SetContext(IClientChannel channel,

         IDictionary ctx)

            IContextManager cm = channel.GetProperty();

            if (cm != null)

                cm.SetContext(ctx);

Step 10: In the main method, I was creating the proxy for the service and calling the Add operation. Call to this method will add instance state to the database. Now I have closed the proxy and creating new proxy instance. When I call the Subtract and Multiply operation, it will operate on the previously saved value (instance state).

static void Main(string[] args)

             //Create the proxy for the service

            SimpleCalculatorService.SimpleCalculatorClient client

            = new SimpleCalculatorService.SimpleCalculatorClient

            "WSHttpContextBinding_ISimpleCalculator");

            int currentValue = 0;

            //Call the Add method from the service

            currentValue = client.Add(10000);

            Console.WriteLine("The current value is {0}", currentValue);

            //Save the Context from the service to the client

           Helper.SaveContext(client.InnerChannel);

            //Close the proxy

            client.Close();

            //Create new Instance of the proxy for the service

            client = new SimpleCalculatorService.SimpleCalculatorClient

            ("WSHttpContextBinding_ISimpleCalculator");

            //Load the context from the client to start from saved state

            IDictionary cntx=Helper.LoadContext();

            //Set Context to context manager

            Helper.SetContext(client.InnerChannel, cntx);

            //Call the Subtract and Multiply method from service

            currentValue = client.Subtract(2);

            Console.WriteLine("The current value is {0}", currentValue);

            currentValue = client.Multiply(5);

            Console.WriteLine("The current value is {0}", currentValue);

            //Delete the context from the client

            Helper.DeleteContext();

            //Remove persistance state from the server

            client.EndPersistence();

            Console.WriteLine("Press  to shut down the client.");

            Console.ReadLine();

            client.Close();

Throttling

WCF throttling provides some properties that you can use to limit how many instances or sessions are created at the application level. Performance of the WCF service can be improved by creating proper instance.

Attribute	Description
maxConcurrentCalls	Limits the total number of calls that can currently be in progress across all service instances. The default is 16.
maxConcurrentInstances	The number of InstanceContext objects that execute at one time across a ServiceHost. The default is Int32.MaxValue.
maxConcurrentSessions	A positive integer that limits the number of sessions a ServiceHost object can accept. The default is 10.

Service Throttling can be configured either Adminstractive or Programatically

Administrative(configuration file)

Using tag of the Service Behavior, you can configure the maxConcurrentCalls, maxConcurrentInstances , maxConcurrentSessions property as shown below.

<system.serviceModel>

    <services >

      <service behaviorConfiguration="ServiceBehavior"  name="MyService">

        <endpoint address="" binding="wsHttpBinding" contract="IMyService">

          <identity>

            <dns value="localhost"/>

          </identity>

        </endpoint>

        <endpoint address="mex" binding="mexHttpBinding" contract="IMetadataExchange"/>

      </service>

    </services>

    <behaviors>

      <serviceBehaviors>

        <behavior name="ServiceBehavior">

          <serviceMetadata httpGetEnabled="true"/>

          <serviceDebug includeExceptionDetailInFaults="true "/>

          <serviceThrottling maxConcurrentCalls="500"

 maxConcurrentInstances ="100"

maxConcurrentSessions ="200"/>

        </behavior>

      </serviceBehaviors>

    </behaviors>

  </system.serviceModel>

Programming Model

Use ServiceThrottlingBehavior object to set concurrent calls, session and instance property.

           ServiceHost host = new ServiceHost(typeof(MyService));

           ServiceThrottlingBehavior throttle

 = host.Description.Behaviors.Find();

            if (throttle == null)

                throttle = new ServiceThrottlingBehavior();

                throttle.MaxConcurrentCalls = 500;

                throttle.MaxConcurrentSessions = 200;

                throttle.MaxConcurrentInstances = 100;

                host.Description.Behaviors.Add(throttle);

            host.Open();

Operations

In classic object or component- oriented programming model offered only single way for client to call a method. Client will issue a call, block while the call was in progress, and continue executing once the method returned.
WCF will support classical Request-Replay model, along with that it also supports One-Way call(call and forget operation) and callback(service to call back the client)
Three modes of communication between client and service are

Request-Reply

By default all WCF will operated in the Request-Replay mode. It means that, when client make a request to the WCF service and client will wait to get response from service (till receiveTimeout). After getting the response it will start executing the rest of the statement. If service doesn't respond to the service within receiveTimeout, client will receive TimeOutException.
Apart from NetPeerTcpBinding and the NetMsmqBinding all other bindings will support request-reply operations.

One-Way

In One-Way operation mode, client will send a request to the server and does not care whether it is success or failure of service execution. There is no return from the server side, it is one-way communication.
Client will be blocked only for a moment till it dispatches its call to service. If any exception thrown by service will not reach the server.
Client can continue to execute its statement, after making one-way call to server. There is no need to wait, till server execute. Sometime when one-way calls reach the service, they may not be dispatched all at once but may instead be queued up on the service side to be dispatched one at a time, according to the service's configured concurrency mode behavior. If the number of queued messages has exceeded the queue's capacity, the client will be blocked even if it's issued a one-way call. However, once the call is queued, the client will be unblocked and can continue executing, while the service processes the operation in the background.

Definition :

One-way operation can be enabled by setting IsOneWay property to true in Operation contract attribute.

[ServiceContract]

public interface IMyService

    [OperationContract(IsOneWay=true)]

    void MyMethod(EmployeeDetails emp);

One-Way Operations and Sessionful Services

Let us see the example, what will happen when you use the one-way communication with Sessionful service.

    [ServiceContract(SessionMode = SessionMode.Required)]

    interface IMyContract

        [OperationContract(IsOneWay = true)]

        void MyMethod();

As per above configuration, when client makes one-way call using MyMethod() operation and if it close the proxy. Client will be blocked until operation completes. It will be good practice, that one-way operation should be applied on per-call and singleton service.
Suppose If you want to make use of One-way operation in Sessionful service, use in the last operation of the service which will terminate the session. This operation should not return any value.

    [ServiceContract(SessionMode = SessionMode.Required)]

    interface IMyContract

        [OperationContract]

        void MyMethod1();

        [OperationContract]

        string MyMethod2();

        [OperationContract(IsOneWay = true, IsInitiating = false,

                                           IsTerminating = true)]

        string CloseSessionService(int id);

One-Way Operations and Exceptions

Suppose when we are using BasicHttpBinding or WSHttpBinding, i.e. no transport session is used, if any exception throw by service will not affect the client. Client can make a call to the service using same proxy

[ServiceContract]

interface IMyContract

   [OperationContract(IsOneWay = true)]

   void MethodWithError( );

   [OperationContract]

   void MethodWithoutError( );

//Client side without transport session

MyContractClient proxy = new MyContractClient( );

proxy.MethodWithError( ); //No exception is thrown from serivce

proxy.MethodWithoutError( ); //Operation will execute properly

proxy.Close( );

In the presence of transport session, any exception thrown by service will fault the client channel. Client will not be able to make new call using same proxy instance.

//Client side transport session

MyContractClient proxy = new MyContractClient( );

proxy.MethodWithError( );

proxy.MethodWithoutError( ); //Can not executre because channel is faulted

proxy.Close( );

Callback Service

Till now we have seen that the all clients will call the service to get the things done. But WCF also provides the service to call the client. In which, service will act as client and client will act as service.

HTTP protocols are connectionless nature, so it is not supported for callback operation. So BasicHttpBinding and WSHttpBinding cannot be used for this operation.
WCF support WSDualHttpBinding for call back operation.
All TCP and IPC protocols support Duplex communication. So all these binding will be used for callback operation.

Defining and configuring a callback contract

Callback service can be enabled by using CallbackContract property in the ServiceContract attribute. In the below example you can find the decalration of the callback contract and it is configured in the ServiceContract attribute.

    public interface IMyContractCallback

        [OperationContract]

        void OnCallback();

    [ServiceContract(CallbackContract = typeof(IMyContractCallback))]

    public interface IMyContract

        [OperationContract()]

        void MyMethod();

Client Callback Setup

As I said earlier, in callback operation client will act as service and service will act as client. So client has to expose a callback endpoint to the service to call. In the earlier part of the tutorial I have mention that InstanceContext is the execution scope of inner most service instance. It provides a constructor that takes the service instance to the host.

        IMyContractCallback callback=new MyCallback();

        InstanceContext cntx=new InstanceContext(callback);

        MyServiceClient proxy = new MyServiceClient(cntx);

        proxy.MyMethod();

The client must use a proxy that will set up the bidirectional communication and pass the callback endpoint reference to the service. This can be achieved by creating the proxy using DuplexClientBase

   class MyServiceClient:DuplexClientBase,IMyContract

        public MyServiceClient(InstanceContext callbackCntx)

            : base(callbackCntx)

        public void MyMethod()

             base.Channel.MyMethod();

Service-Side Callback Invocation

The client-side callback endpoint reference is passed along with every call the client makes to the service, and it is part of the incoming message. The OperationContext class provides the service with easy access to the callback reference via the generic method GetCallbackChannel( ). Service can call the client side callback method using reference e to the client side callback instance. The following code shows the callback method invocation.

IMyContractCallback

 callbackInstance=OperationContext.Current.GetCallbackChannel();

            callbackInstance.OnCallback();

How to Create Callback Service in WCF

This tutorial gives hands-on to create a sample Callback service.
Step 1: Create the sample Classlibrary project using Visual Studio 2008 and name it as CallbackService

Step 2 : Add System.ServiceModel reference to the project
Step 3: Create the Callback and Service contract as shown below. You need to mention CallbackContract property in the ServiceContract attribute. Implementation of the Callback contract will be done on the client side.

IMyContract.cs

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.ServiceModel;

namespace CallbackService

    public interface IMyContractCallback

        [OperationContract]

        void OnCallback();

    [ServiceContract(CallbackContract = typeof(IMyContractCallback))]

    public interface IMyContract

        [OperationContract()]

        void MyMethod();

Step 4: Implement the Service contract as shown below. In the below code you will find using OperationContext is used to receive the reference to Callback instance. Using that instance we are calling the OnCallback() method from client side.

MyService.cs

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.ServiceModel;

namespace CallbackService

    [ServiceBehavior(ConcurrencyMode=ConcurrencyMode.Multiple )]

   public class MyService:IMyContract

        public void MyMethod()

            //Do something

            IMyContractCallback callbackInstance

            =OperationContext.Current.GetCallbackChannel();

            callbackInstance.OnCallback();

You can also note that We have set the ConcurrencyMode to Multile. If you are not using ConcurrencyMode to Multiple or Reentent, you will be end up with deadlock exception as shown below. This is because when a client made a call to the service, channel is created and lock by WCF service. If you are calling the Callback method inside the service method. Service will try to access the lock channel, this may leads to deadlock. So you can set ConcurrencyMode to Multiple or Reentent so it will release the lock silently.

Step 5: Create a Console application using Visual Studio 2008 and name it a CallbackServiceHost. This application is used to self-host the WCF service

Step 6: Main method

        static void Main(string[] args)

            Uri httpUrl = new Uri("http://localhost:8090/MyService/");

             ServiceHost host = new ServiceHost(typeof(CallbackService.MyService), httpUrl);

            host.Open();

            Console.WriteLine("Service is Hosted at {0}", DateTime.Now.ToString());

            Console.WriteLine("Host is running...Press  key to stop the service.");

            Console.ReadLine();

            host.Close();

Step 7: Use Duplex binding to support Callback operation.

Web.Config

<system.serviceModel>

    <services >

      <service behaviorConfiguration="ServiceBehavior"

      name="CallbackService.MyService">

        <endpoint address="http://localhost:8090/MyService"

        binding="wsDualHttpBinding" contract="CallbackService.IMyContract">

          <identity>

            <dns value="localhost"/>

          </identity>

        </endpoint>

        <endpoint address="mex"

        binding="mexHttpBinding" contract="IMetadataExchange"/>

      </service>

    </services>

    <behaviors>

      <serviceBehaviors>

        <behavior name="ServiceBehavior">

          <serviceMetadata httpGetEnabled="true"/>

          <serviceDebug includeExceptionDetailInFaults="true "/>

        </behavior>

      </serviceBehaviors>

    </behaviors>

  </system.serviceModel>

Step 8: Run the host application

Step 9: Create Console Application using Visual Studio 2008 and name it as CallbackClient. This is the client application which contain Callback implementation.

Step10: Add System.ServiceModel and CallbackService as reference to the project
Step 11: Create the proxy class as shown below. Use DuplexClientBase to create the proxy, because it will support bidirectional communication. Create the contractor which will accept InstanceContext as parameter.

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.ServiceModel;

using CallbackService;

namespace CallbackClient

    class MyServiceClient:DuplexClientBase,IMyContract

        public MyServiceClient(InstanceContext callbackCntx)

            : base(callbackCntx)

        public void MyMethod()

             base.Channel.MyMethod();

Step12: Create the implementation for Callback Contract

class MyCallback : IMyContractCallback

        public void OnCallback()

            Console.WriteLine("Callback method is called from client side.");

Thursday, December 15, 2011

ABC of WCF

ABC of WCF

Address

Binding

Contract

Example:

Binding and Behavior

Binding

Example:

Contracts and Service Host

Contracts

Service Contract

Data Contract

Message Contract

Fault Contract

Service Host

Message and Channel

Message

WCF Runtime

Channels:

Transport Channels

Protocol Channels

WCF Client and Metadata

WCF Client

Metadata

WCF Architecture

Contracts

Service contracts

Data contract

Message Contract

Policies and Binding

Service Runtime

Messaging

Activation and Hosting

WCF Hosting

IIS 5/6 Hosting

Self Hosting

Windows Activation Service

Enable WCF for non-http protocols

Create WAS hosted service

Enable different binding to the hosted service

Windows Service Hosting

Binding

Bindings and Channel Stacks

Types of Binding

BasicHttpBinding

WSHttpBinding

WSDualHttpBinding

WSFederationHttpBinding

NetTcpBinding

NetNamedPipeBinding

NetMsmqBinding

NetPeerTcpBinding

Binding configuration

Administrative (Configuration file):

Programming Model:

Metadata Exchange

Exporting Service Metadata

Publishing Service Metadata

Retrieving Service Metadata

HTTP_GET Enabled Metadata

Administrative (Configuration file):

Progarmming Model:

Metadata Exchange Endpoint

Address

Binding

Contract

Administrative (Configuration file):

Programming Model:

Contracts

Service Contract

Data Contract

Client side

Message Contract

Message

Message Pattern

What is Message contract?

Defining Message Contract

Rules :