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.IEndpointBehavior allows you to change behavior at the endpoint level. System.ServiceModel.Description.IContractBehavior allows 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();  
<?xml version="1.0" encoding="utf-8" ?>  
            <endpoint address="http://localhost:8080/SimpleService/"
          <behavior name="clientInspectorsAdded">  
            <simpleBehaviorExtension />  
            type="SimpleServiceLib.SimpleBehaviorExtensionElement, Host, Version=, Culture=neutral, PublicKeyToken=null"/>  

See also