Metadata Exchange Endpoint

Exposing the metadata using HTTP-GET has a disadvantage, such that there is no guarantee that other platforms you interact will support it. There is other way of exposing the using special endpoint is called as Metadata Exchange Endpoint. You can have as many metadata exchange endpoints as you want.

Address

It is basically Uri to identify the metadata. You can specify as address in the endpoint but append with "mex" keyword. For example "http://localhost:9090/MyCalulatorService/mex"

Binding

There are four types of bindings supported for metadata exchange. They are mexHttpBinding, mexHttpsBinding, mexNamedPipesBinding, mexTcpBinding.

Contract

IMetadataExchange is the contract used for MEX endpoint. WCF service host automatically provides the implementation for this IMetadataExcahnge while hosting the service.

You can create the Metadata Exchange Endpoint either Administrative (configuration file) or programmatically.

Administrative (Configuration file):

In the configuration file of the hosting application, you can add metadata exchange endpoint as shown below.

<system.serviceModel>
<services>
 <service name="MyService">
 <endpoint address="http://localhost/IISHostedService/MyService.svc"
 binding="wsHttpBinding" contract="IMyService">
 <identity>
 <dns value="localhost"/>
 </identity>
 </endpoint>
 <endpoint address="mex" binding="mexHttpBinding" contract="IMetadataExchange"/>
 </service>
</services>  
</system.serviceModel>

Programming Model:

In the following code I have mention about creating the Metadata Exchange Endpoint through coding. Steps to create the metadata endpoint are

• Create the ServiceMetadataBehavior object and add to Service host description.

ServiceMetadataBehavior smb = new ServiceMetadataBehavior();
            host.Description.Behaviors.Add(smb);

• Create the metadata binding object using MetadataExchangeBinding

Binding mexBinding = MetadataExchangeBindings.CreateMexHttpBinding ();

• 3. Add the endpoint to the service host with address, binding and contract.

host.AddServiceEndpoint(typeof(IMetadataExchange), mexBinding, "mex");

Complete code for hosting the service with metadata exchange endpoint is shown below.

//Create a URI to serve as the base address
            Uri httpUrl = new Uri("http://localhost:8090/MyService/SimpleCalculator");
            //Create ServiceHost
            ServiceHost host = new 
            ServiceHost(typeof(MyCalculatorService.SimpleCalculator), httpUrl);
            //Add a service endpoint
            host.AddServiceEndpoint
            (typeof(MyCalculatorService.ISimpleCalculator), new WSHttpBinding(), "");
            //Enable metadata exchange
            ServiceMetadataBehavior smb = new ServiceMetadataBehavior();
            host.Description.Behaviors.Add(smb);
            Binding mexBinding = MetadataExchangeBindings.CreateMexHttpBinding ();
            //Adding metadata exchange endpoint
            host.AddServiceEndpoint(typeof(IMetadataExchange), mexBinding, "mex");
            //Start the Service
            host.Open();

            Console.WriteLine("Service is host at " + DateTime.Now.ToString());
            Console.WriteLine("Host is running... Press  key to stop");