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How to: Inspect and Modify Messages on the Service

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You can inspect or modify the incoming or outgoing messages across a Windows Communication Foundation (WCF) client by implementing a System.ServiceModel.Dispatcher.IDispatchMessageInspector and inserting it into the service runtime. For more information, see Extending Dispatchers. The equivalent feature on the service is the System.ServiceModel.Dispatcher.IClientMessageInspector.

To inspect or modify messages

  1. Implement the System.ServiceModel.Dispatcher.IDispatchMessageInspector interface.

  2. Implement a System.ServiceModel.Description.IServiceBehavior, System.ServiceModel.Description.IEndpointBehavior, or System.ServiceModel.Description.IContractBehavior interface depending upon the scope at which you want to easily insert your service message inspector.

  3. Insert your behavior prior to calling the ICommunicationObject.Open method on the System.ServiceModel.ServiceHost. For details, see Configuring and Extending the Runtime with Behaviors.

Example

The following code examples show, in order:

  • A service inspector implementation.

  • A service behavior that inserts the inspector.

  • A configuration file that loads and runs the behavior in a service application.

#region IDispatchMessageInspector Members
public object AfterReceiveRequest(ref System.ServiceModel.Channels.Message request, IClientChannel channel, InstanceContext instanceContext)
{
  Console.WriteLine("IDispatchMessageInspector.AfterReceiveRequest called.");
  return null;
}

public void BeforeSendReply(ref System.ServiceModel.Channels.Message reply, object correlationState)
{
  Console.WriteLine("IDispatchMessageInspector.BeforeSendReply called.");
}
#endregion

#Region "IDispatchMessageInspector Members"
        Public Function AfterReceiveRequest(ByRef request As System.ServiceModel.Channels.Message, _
                           ByVal channel As IClientChannel, ByVal instanceContext As InstanceContext) _
                           As Object Implements IDispatchMessageInspector.AfterReceiveRequest
            Console.WriteLine("IDispatchMessageInspector.AfterReceiveRequest called.")
            Return Nothing
        End Function

        Public Sub BeforeSendReply(ByRef reply As System.ServiceModel.Channels.Message, ByVal correlationState As Object) _
        Implements IDispatchMessageInspector.BeforeSendReply
            Console.WriteLine("IDispatchMessageInspector.BeforeSendReply called.")
        End Sub
#End Region

#region IServiceBehavior Members
public void AddBindingParameters(
  ServiceDescription serviceDescription,
  ServiceHostBase serviceHostBase,
  System.Collections.ObjectModel.Collection<ServiceEndpoint> endpoints,
  BindingParameterCollection bindingParameters
)
{ return; }

public void ApplyDispatchBehavior(ServiceDescription serviceDescription, ServiceHostBase serviceHostBase)
{
  foreach (ChannelDispatcher chDisp in serviceHostBase.ChannelDispatchers)
  {
    foreach (EndpointDispatcher epDisp in chDisp.Endpoints)
    {
      epDisp.DispatchRuntime.MessageInspectors.Add(new Inspector());
      foreach (DispatchOperation op in epDisp.DispatchRuntime.Operations)
        op.ParameterInspectors.Add(new Inspector());
    }
  }
}

#Region "IServiceBehavior Members"
        Public Sub AddBindingParameters(ByVal serviceDescription As ServiceDescription, _
                       ByVal serviceHostBase As ServiceHostBase, ByVal endpoints As _
                       System.Collections.ObjectModel.Collection(Of ServiceEndpoint), _
                       ByVal bindingParameters As BindingParameterCollection) Implements IServiceBehavior.AddBindingParameters
            Return
        End Sub

        Public Sub ApplyDispatchBehavior(ByVal serviceDescription As ServiceDescription, _
                                         ByVal serviceHostBase As ServiceHostBase) Implements _
                                         IServiceBehavior.ApplyDispatchBehavior
            For Each chDisp As ChannelDispatcher In serviceHostBase.ChannelDispatchers
                For Each epDisp As EndpointDispatcher In chDisp.Endpoints
                    epDisp.DispatchRuntime.MessageInspectors.Add(New Inspector())
                    For Each op As DispatchOperation In epDisp.DispatchRuntime.Operations
                        op.ParameterInspectors.Add(New Inspector())
                    Next op
                Next epDisp
            Next chDisp
        End Sub

<configuration>
  <system.serviceModel>
    <services>
      <service 
        name="Microsoft.WCF.Documentation.SampleService"
        behaviorConfiguration="metadataSupport">
        <host>
          <baseAddresses>
            <add baseAddress="http://localhost:8080/SampleService" />
          </baseAddresses>
        </host>
        <endpoint
          address=""
          binding="wsHttpBinding"
          contract="Microsoft.WCF.Documentation.ISampleService"
        />
        <endpoint
           address="mex"
           binding="mexHttpBinding"
           contract="IMetadataExchange"
        />
      </service>
    </services>
    <behaviors>
      <serviceBehaviors>
        <behavior name="metadataSupport">
          <serviceMetadata httpGetEnabled="true" httpGetUrl=""/>
          <serviceInterceptors />
        </behavior>
      </serviceBehaviors>
    </behaviors>
    <extensions>
      <behaviorExtensions>
        <add 
          name="serviceInterceptors" 
          type="Microsoft.WCF.Documentation.InspectorInserter, HostApplication, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null"
        />
      </behaviorExtensions>
    </extensions>
  </system.serviceModel>
</configuration>

See also