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Saturday, 17 September 2011


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. IIS Screen shot
This screen will appear when we run the application.
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();

        }
Step 9: If we run the application we will find the output as shown below.
I hope you have enjoyed the Service hosted in IIS. Now let start the look on the self hosted service.
BASICS ON WCF: INTRODUCTION



WCF Architecture(windowsclient.net)

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
  • IIS 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).

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