Lesson 3: WCF Extensibility in C#.NET

Create Data Matrix ECC200 in C#.NET Lesson 3: WCF Extensibility

public void ApplyClientBehavior(ServiceEndpoint endpoint, ClientRuntime clientRuntime) { MessageLogInspector inspector = new MessageLogInspector(); clientRuntime.MessageInspectors.Add(inspector); } public void ApplyDispatchBehavior(ServiceEndpoint endpoint, EndpointDispatcher endpointDispatcher) { MessageLogInspector inspector = new MessageLogInspector(); endpointDispatcher.DispatchRuntime.MessageInspectors.Add(inspector); } public void Validate(ServiceEndpoint endpoint) { } }

Now that you have a behavior, it needs to be added to a behavior extension. After the behavior is added to such an extension, it can be added to the WCF pipeline through the configuration file. The behavior extension is actually a class that derives from the BehaviorExtensionElement class, and the minimum functionality for the class is to override the CreateBehavior method so that it returns an instance of the desired behavior. The following code demonstrates this, using the LoggingEndpointBehavior:

' VB Public Class LoggingBehaviourExtensionElement Inherits BehaviorExtensionElement Public Overrides ReadOnly Property BehaviorType() As Type Get Return GetType(LoggingEndpointBehavior) End Get End Property Protected Overrides Function CreateBehavior() As Object Return New LoggingEndpointBehavior (); End Function End Class // C# public class LoggingBehaviorExtensionElement : BehaviorExtensionElement { public override Type BehaviorType { get { return typeof(LoggingEndpointBehavior); } }

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protected override object CreateBehavior() { return new LoggingEndpointBehavior(); } }

After the behavior extension is implemented, you can add the behavior (which is a message inspector) by adding a behaviorExtension element in the extensions section of the serviceModel element. After the extension has been referenced, you can add it to an endpointBehavior element as shown in bold in the following code:

<system.serviceModel> <behaviors> <endpointBehaviors> <behavior name="LoggingEndpointBehavior"> <messageLogger /> </behavior> </endpointBehaviors> </behaviors> <extensions> <behaviorExtensions> <add name="messageLogger" type="assembly.LoggingBehaviorExtensionElement, assembly, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null"/> </behaviorExtensions> </extensions> </system.serviceModel>

You might notice the fully qualified assembly name in the behaviorExtensions tag. This is a requirement, at least at the moment. If the type name is not fully qualified, a ConfigurationErrorsException exception is thrown. In fact, in what some consider to be a bug, the type name is actually white space sensitive. If you removed any of the spaces from the type name, the same ConfigurationErrorsException is thrown. Exam Tip

You ll notice from the example that the name of the behavior extension matches the name of the node within the behavior. This is required for the extension to function properly.

Alternatively, the behavior can be added imperatively by accessing the endpoint behaviors through the proxy object. Making the assumption that the proxy class is called UpdateServiceClient, the following code will added to the just created logging message inspector:

' VB Dim client As New UpdateServiceClient() client.Endpoint.Behaviors.Add(New LoggingEndpointBehavior()) // C# UdpateServiceClient client = new UpdateServiceClient(); client.Endpoint.Behaviors.Add(new LoggingEndpointBehavior());

In this lab, you will explore some of the extensibility points exposed by WCF. In particular, you will use the parameter inspection technique to validate that a particular parameter matches a regular expression pattern. You will also use message inspection to send the contents of the request and response message to an output window. Exercise 1 Use Message Inspection In this first exercise, you will use message inspection to direct a copy of the request and response messages to an output window. The purpose of the exercise is to demonstrate how you can use inspection to access the message. When accessed, you can modify the message prior to sending it, including adding information or changing the format. 1. Navigate to the <InstallHome>/6/Lesson3/Exercise1/<language>/Before directory and double-click the Exercise1.sln file to open the solution in Visual Studio. The solution consists of two projects. They are as follows: The DemoService project, a simple WCF service library that implements the IContact interface. This interface consists of a single method (UpdatePhone) that retrieves some information about the headers in the message sent to the service. For this exercise, the method displays the phone number that has been passed into the method in the trace output. The TestClient project, a Console application that enables you to consume the DemoService service. This client is the target of the message inspector injection. 2. In Solution Explorer, right-click the TestClient project. Select Add and then Class from the context menu. 3. In the Add New Item dialog box, change the name to MessageTracer and click Add. 4. Add the following statements to the top of the file:

' VB Imports System.ServiceModel.Dispatcher Imports System.ServiceModel.Channels Imports System.ServiceModel // C# using System.ServiceModel.Dispatcher; using System.ServiceModel.Channels; using System.ServiceModel;

The MessageTracer class is the implementation of the inspection. As such, it needs to implement the IClientMessageInspector interface. 5. Change the class declaration to be the following: