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How to: Inspect or Modify Messages on the Client

You can inspect or modify the incoming or outgoing messages across a WCF client by implementing a System.ServiceModel.Dispatcher.IClientMessageInspector and inserting it into the client runtime. For more information, see Extending Clients. The equivalent feature on the service is the System.ServiceModel.Dispatcher.IDispatchMessageInspector. For a complete code example see the Message Inspectors sample.

To inspect or modify messages

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

  2. Implement a System.ServiceModel.Description.IEndpointBehavior or System.ServiceModel.Description.IContractBehavior depending upon the scope at which you want to insert the client message inspector. System.ServiceModel.Description.IEndpointBehaviorallows you to change behavior at the endpoint level. System.ServiceModel.Description.IContractBehaviorallows you to change behavior at the contract level.

  3. Insert the behavior prior to calling the ClientBase<TChannel>.Open or the ICommunicationObject.Open method on the System.ServiceModel.ChannelFactory<TChannel>. For details, see Configuring and Extending the Runtime with Behaviors.

The following code examples show, in order:

  • A client inspector implementation.

  • An endpoint behavior that inserts the inspector.

  • A BehaviorExtensionElement- derived class that allows you to add the behavior in a configuration file.

  • A configuration file that adds the endpoint behavior which inserts the client message inspector into the client runtime.

// Client message inspector
public class SimpleMessageInspector : IClientMessageInspector
{
    public void AfterReceiveReply(ref System.ServiceModel.Channels.Message reply, object correlationState)
    {
        // Implement this method to inspect/modify messages after a message
        // is received but prior to passing it back to the client 
        Console.WriteLine("AfterReceiveReply called");
    }

    public object BeforeSendRequest(ref System.ServiceModel.Channels.Message request, IClientChannel channel)
    {
        // Implement this method to inspect/modify messages before they 
        // are sent to the service
        Console.WriteLine("BeforeSendRequest called");
        return null;
    }
}

// Endpoint behavior
public class SimpleEndpointBehavior : IEndpointBehavior
{
    public void AddBindingParameters(ServiceEndpoint endpoint, System.ServiceModel.Channels.BindingParameterCollection bindingParameters)
    {
         // No implementation necessary
    }

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

    public void ApplyDispatchBehavior(ServiceEndpoint endpoint, EndpointDispatcher endpointDispatcher)
    {
         // No implementation necessary
    }

    public void Validate(ServiceEndpoint endpoint)
    {
         // No implementation necessary
    }
}
// Configuration element 
public class SimpleBehaviorExtensionElement : BehaviorExtensionElement
{
    public override Type BehaviorType
    {
        get { return typeof(SimpleEndpointBehavior); }
    }

    protected override object CreateBehavior()
    {
         // Create the  endpoint behavior that will insert the message
         // inspector into the client runtime
        return new SimpleEndpointBehavior();
    }
}

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