Automatic Format Selection

This sample demonstrates how to enable automatic format selection (XML or JSON) with the Windows Communication Foundation (WCF) REST programming model, as well as how to explicitly set the format in the operation code.

Sample Details

The sample consists of a service along with client code that makes requests to the service. The service supports a single HTTP GET operation (EchoWithGet) and a single HTTP POST operation (EchoWithPost). Both operations expect a string and then return the string in the response. With the GET operation, the string is provided in a URI query-string parameter. With the POST operation, the string is provided in the body of the request, serialized in XML. The service is able to return responses in either XML or JSON, utilizing the new automatic format selection and imperative format selection features in .NET Framework version 4.

In the sample, automatic format selection is enabled using the App.config file. On the default Web HTTP endpoint, the automaticFormatSelectionEnabled attribute has been given a value of true. With automatic format selection enabled, the WCF infrastructure selects the most appropriate response format (XML or JSON) given the HTTP Accept or Content-Type headers of the request. The developer is not required to provide any additional code or configuration other than setting the automaticFormatSelectionEnabled attribute to true to use this new feature. In the client code in Program.cs, requests are sent to both the GET and POST operations of the service with the HTTP Accept header specified as either “application/xml” or “application/json” and the service returns a response in that respective format.

Also in the GET operation, imperative format selection is used. The GET operation checks for an optional format query-string parameter and if present, sets the response format on the OutgoingResponse property. Imperatively setting the response format in this way overrides the automatic format selection done by the WCF infrastructure.

The sample consists of a self-hosted service and a client that runs within a console application. As the console application runs, the client makes requests to the service and writes the pertinent information from the responses to the console window.

To use this sample

1. Open the solution for the Automatic Format Selection Sample. When launching Visual Studio 2010, you must run as an administrator for the sample to execute successfully. Do this by right-clicking the Visual Studio 2010 icon and select Run as Administrator from the context menu.

2. Press CTRL+SHIFT+B to build the solution and then press Ctrl+F5 to run the console application AutomaticFormatSelection project. The console window appears and provides the URI of the running service and the URI of the HTML help page for the running service.

3. As the sample runs, the client sends requests to the service and writes the responses to the console window. Notice the different formats of the responses in XML and JSON.

4. Press any key to terminate the sample.

Note:

The samples may already be installed on your machine. Check for the following (default) directory before continuing. <InstallDrive>:\WF_WCF_Samples If this directory does not exist, go to Windows Communication Foundation (WCF) and Windows Workflow Foundation (WF) Samples for .NET Framework 4 to download all Windows Communication Foundation (WCF) and WF samples. This sample is located in the following directory. <InstallDrive>:\WF_WCF_Samples\WCF\Basic\Web\AutomaticFormatSelection