So my previous post looked at adding data into the headers of the WCF service calls from the client-side perspective.

Ofcourse for this to be of any use we need the service to handle the extraction of this header data. So this post is mean’t to cover the basics of this. First we need to create the extension, so we inherit from BehaviorExtensionElement (just as we did on the client)

public class SecurityTokenEndpointBehaviourExtensionElement : BehaviorExtensionElement
{
   public override Type BehaviorType
   {
      get { return typeof(SecurityTokenServiceBehaviour); }
   }
   protected override object CreateBehavior()
   {
      return new SecurityTokenServiceBehaviour();
   }
}

Now we need to create an implementation of the IServiceBehavior (on the client this is the IEndpointBehavior)

public class SecurityTokenServiceBehaviour : IServiceBehavior
{
   public void Validate(ServiceDescription serviceDescription, 
                        ServiceHostBase serviceHostBase)
   {
   }

   public void AddBindingParameters(ServiceDescription serviceDescription, 
                         ServiceHostBase serviceHostBase, 
                         Collection<ServiceEndpoint> endpoints, 
                         BindingParameterCollection bindingParameters)
   {
   }

   public void ApplyDispatchBehavior(ServiceDescription serviceDescription, 
                         ServiceHostBase serviceHostBase)
   {
      foreach(ChannelDispatcher cd in serviceHostBase.ChannelDispatchers)
      {
         foreach(EndpointDispatcher epd in cd.Endpoints)
         {
            epd.DispatchRuntime.MessageInspectors.Add(new SecurityTokenMessageInspector());
         }
      }
   }
}

and finally we implement an IDispatchMessageInspector (on the client this would be the IClientMessageInspector)

public class SecurityTokenMessageInspector : IDispatchMessageInspector
{
   public object AfterReceiveRequest(ref Message request, 
                     IClientChannel channel, 
                     InstanceContext instanceContext)
   {
      return null;
   }

   public void BeforeSendReply(ref Message reply, object correlationState)
   {
   }
}

Okay so we’ve got all the code in place but now we need to tie this into WCF using the configuration (ofcourse if you prefer you can do this in code).

Just as we need to do in the client, we need to register the extension in an extensions element and again as per the client we then need to link the behaviour to the extension, see the App.config for this service below

<system.serviceModel>
   <behaviors>
      <serviceBehaviors>
         <behavior name="MyBehavior">
            <serviceMetadata httpGetEnabled="true" />
            <serviceDebug includeExceptionDetailInFaults="true" />
            <!--our extension -->
            <securityTokenExtension /> 
         </behavior>
      </serviceBehaviors>
   </behaviors>
   <services>
      <service behaviorConfiguration="MyBehavior" name="SimpleService.MyService">
        <endpoint address="MyService" binding="basicHttpBinding"
          bindingConfiguration="" contract="SimpleService.IMyService" />
        <host>
          <baseAddresses>
            <add baseAddress="http://localhost:9095/" />
          </baseAddresses>
        </host>
      </service>
   </services>
   <extensions>
      <behaviorExtensions>
        <add name="securityTokenExtension" 
           type="SimpleService.SecurityTokenEndpointBehaviourExtensionElement, SimpleService" />
      </behaviorExtensions>
   </extensions>
</system.serviceModel>

Finally, how do we get the value stored in the header on the service ?

The following code shows how we extract the value from the header named “myToken”, the generic argument shown in the method call GetHeader represents the type we expect the data to be.

public object AfterReceiveRequest(ref Message request, 
                  IClientChannel channel, 
                  InstanceContext instanceContext)
{
   int idx = request.Headers.FindHeader("myToken", String.Empty);
   if(idx >= 0)
   {
      Console.WriteLine(String.Format("Header value: {0}", 
                       request.Headers.GetHeader<string>(idx));
   }
   return null;
}

When working with WCF you may find a need to add data to the message headers, for example maybe you wish to add some form of authentication token or the likes.

The first thing we need to do is create a BehaviorExtensionElement and add the relevant configuration to the App.Config.

public class SecurityTokenEndpointBehaviourExtensionElement : BehaviorExtensionElement
{
   public override Type BehaviorType
   {
      get { return typeof(SecurityTokenEndpointBehaviour); }
   }
   protected override object CreateBehavior()
   {
      return new SecurityTokenEndpointBehaviour();
   }
}

Now we need the corresponding entry in the config file for the extension and also the behaviour that our endpoint will map to

<behaviors>
   <endpointBehaviors>
      <behavior name="serviceEndpointBehaviour">
         <securityTokenExtension />
      </behavior>
   </endpointBehaviors>
</behaviors>
<extensions>
   <behaviorExtensions>
      <add name="securityTokenExtension"
	type="PutridParrot.SecurityTokenEndpointBehaviourExtensionElement, PutridParrot" />
   </behaviorExtensions>
</extensions>

As you can see the configuration basically tells WCF to use our BehaviorExtensionElement which then creates the behaviour. This behaviour then adds inspectors to the client as in the sample below

public class SecurityTokenEndpointBehaviour : IEndpointBehavior
{
   public void AddBindingParameters(ServiceEndpoint endpoint, 
                   BindingParameterCollection bindingParameters)
   {
   }

   public void ApplyClientBehavior(ServiceEndpoint endpoint, 
                   ClientRuntime clientRuntime)
   {
      clientRuntime.MessageInspectors.Add(new SecurityTokenMessageInspector());
   }

   public void ApplyDispatchBehavior(ServiceEndpoint endpoint, 
                    EndpointDispatcher endpointDispatcher)
   {
   }

   public void Validate(ServiceEndpoint endpoint)
   {
   }
}

So this code is very simple. In this case we’re simply adding a new message inspector and it’s this IClientMessageInspector implementation that adds the token to the WCF headers. As shown below

public class SecurityTokenMessageInspector : IClientMessageInspector
{
   public object BeforeSendRequest(ref Message request, IClientChannel channel)
   {
      request.Headers.Add(MessageHeader.CreateHeader("myToken", 
                          String.Empty, SecurityToken.Token));
      return null;
   }

   public void AfterReceiveReply(ref Message reply, object correlationState)
   {
   }
}

The code above adds a new message header with the name “myToken” and a value of SecurityToken.Token (just assume this is a singleton which creates and stores a security token).

Before this will work on the client we need to configure the end point to use the behaviorConfiguration defined previously, so now in the endpoint add

behaviorConfiguration="serviceEndpointBehaviour"

So the client configuration will look something like

<client>
   <endpoint address="http://localhost:9095/MyService" 
            binding="basicHttpBinding" contract="MyService.IMyService"                    
            behaviorConfiguration="serviceEndpointBehaviour"/>
</client>

Creating a REST style interface with WCF is fairly simple. The steps are listed briefly below, and in more depth below the list of steps.

1. Create your interface/service contract
2. Annotate the methods with WebGet or WebInvoke attributes
3. Create the implementation of the interface
4. Declare the endpoint within the configuration file (or in code). The binding should be webHttpBinding and should have an endpoint behaviour specificied with WebHttp
5. If need be declare the http baseAddress

In more depth

1. Create your interface/service contract
and
2. Annotate the methods with WebGet or WebInvoke attributes

[ServiceContract]
public interface IRestService
{
   [OperationContract]
   [WebGet(UriTemplate = "projects")]
   IList GetProjects();

   [OperationContract]
   [WebGet(UriTemplate = "execute/{projectName}")]
   void Execute(string projectName);
}

Note: Note to self. Don’t forget to put the ServiceContract attribute on the interface !

I’ve implemented both methods a GET methods. Assuming a baseAddress of http://localhost:8733/MyService/ to call these methods through a web browser we can simply type http://localhost:8733/MyService/projects and http://localhost:8733/MyService/execute/MyProject respectively.

3. Create the implementation of the interface

No need to list source code for this, simple implement the interface you created.

4. Declare the endpoint within the configuration file (or in code). The binding should be webHttpBinding and should have an endpoint behaviour specificied with WebHttp
and
5. If need be declare the http baseAddress

The key bit to getting everything to work is the configuration file. I’m self hosting for this example so implementing the code in the App.config

<system.serviceModel>
    <behaviors>
      <serviceBehaviors>
        <behavior name="">
          <serviceMetadata httpGetEnabled="false" />
          <serviceDebug includeExceptionDetailInFaults="false" />
        </behavior>
      </serviceBehaviors>
      <endpointBehaviors>
        <behavior name="rest">
          <webHttp/>
        </behavior>
      </endpointBehaviors>
    </behaviors>
    <services>
      <service name="StandardPlugins.MonitorService">
        <endpoint address="" binding="webHttpBinding" bindingConfiguration=""
            contract="StandardPlugins.IRestService" behaviorConfiguration="rest">
        </endpoint>
        <host>
          <baseAddresses>
            <add baseAddress="http://localhost:8733/MyService/" />
          </baseAddresses>
        </host>
      </service>
    </services>
</system.serviceModel>

Note: The REST methods should be accessible via HTTP, hence the binding is webHttpBinding and the baseAddress is http. A behaviorConfiguration is required with the webHttp element.

Further reading

http://msdn.microsoft.com/en-us/magazine/dd315413.aspx#id0070050
http://msdn.microsoft.com/en-us/library/vstudio/bb412172(v=vs.90).aspx