How can basicHttpBinding, webHttpBinding & mexHttpBinding endpoints coexist in one WCF service

Question

I have a WCF service (target .NET 4) and I need to expose 4 endpoints: SOAP, POX, JSON & MEX.

My configuration file looks like this:

<system.serviceModel>
    <!-- bindings -->
    <bindings>
      <basicHttpBinding>
        <binding name ="soapBinding">
          <security mode="None">
          </security>
        </binding>
      </basicHttpBinding>
      <webHttpBinding>
        <binding name="webBinding">
        </binding>
      </webHttpBinding>
    </bindings>
    <!-- behaviors -->
    <behaviors>
      <endpointBehaviors>
        <!-- plain old XML -->
        <behavior name="poxBehavior">
          <webHttp/>
        </behavior>
        <!-- JSON -->
        <behavior name="jsonBehavior">
          <enableWebScript  />
        </behavior>
      </endpointBehaviors>
      <serviceBehaviors>
        <behavior name="defaultBehavior">
          <serviceDebug includeExceptionDetailInFaults="true" />
          <serviceMetadata httpGetEnabled="true" />
        </behavior>
      </serviceBehaviors>
    </behaviors>
    <services>
      <service name="PubtranService.Service" behaviorConfiguration="defaultBehavior">
        <host>
          <baseAddresses>
            <add baseAddress="http://192.168.1.102:8080/PT/"/>
          </baseAddresses>
        </host>
        <endpoint name="soap"
                  address="soap"
                  binding="basicHttpBinding"
                  bindingConfiguration="soapBinding"
                  contract="PubtranService.IService" />
        <endpoint name="pox"
                  address="pox"
                  binding="webHttpBinding"
                  bindingConfiguration="webBinding"
                  behaviorConfiguration="poxBehavior"
                  contract="PubtranService.IService" />
        <endpoint name="json"
                  address="json"
                  binding="webHttpBinding"
                  bindingConfiguration="webBinding"
                  behaviorConfiguration="jsonBehavior"
                  contract="PubtranService.IService" />
        <endpoint name="mex"
                  address="mex" 
                  binding="mexHttpBinding" 
                  bindingConfiguration=""
                  contract="IMetadataExchange"/>
      </service>
    </services>
  </system.serviceModel>

And when I run the service the WCF Test Client returns failed to add service msg with a System.NullReferenceException - object reference not set to an instance of an object and a stack trace:

System.ServiceModel.Description.ServiceMetadataBehavior.MetadataExtensionInitializer.GenerateMetadata()
System.ServiceModel.Description.ServiceMetadataExtension.EnsureInitialized()   System.ServiceModel.Description.ServiceMetadataExtension.WSMexImpl.GatherMetadata(String dialect, String identifier)   System.ServiceModel.Description.ServiceMetadataExtension.WSMexImpl.Get(Message request)
SyncInvokeGet(Object , Object[] , Object[] )
System.ServiceModel.Dispatcher.SyncMethodInvoker.Invoke(Object instance, Object[] inputs, Object[]& outputs)
System.ServiceModel.Dispatcher.DispatchOperationRuntime.InvokeBegin(MessageRpc& rpc)
System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage5(MessageRpc& rpc)
System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage31(MessageRpc& rpc)
System.ServiceModel.Dispatcher.MessageRpc.Process(Boolean isOperationContextSet)

But the JSON and POX endpoints are accessible and work just fine. On the other hand when I comment them out from the configuration the WCF Test Client properly shows the SOAP service.

At the moment there is only one simple method implemented in the service:

[ServiceContract(Namespace="http://192.168.1.102:8080/")]
public interface IService
{

    [OperationContract]
    [WebGet]
    Tram[] GetOverview(string id);

}

Why do I brake the mex endpoint by adding the pox and json endpoints?

Answer 1

If your aim is to have 1 method to serve for both xml and json i could achieve it as shown below:

<service name ="XMLService.MultipleEndpointService">        
        <endpoint name="soap" address="soap" binding="basicHttpBinding" contract="XMLService.IMultipleEndpointService" />
        <endpoint name="pox" address="pox" binding="webHttpBinding" behaviorConfiguration="web" contract="XMLService.IMultipleEndpointService" />
        <endpoint name="mex" address="mex"  binding="mexHttpBinding" contract="IMetadataExchange"/>
</service>

<endpointBehaviors>
    <behavior name="web">          
      <webHttp/>          
    </behavior>        
 </endpointBehaviors>

Now in your class that implements the Interface i did the following:

public Tram[] GetOverview(string id)
        {
            IList<ContentType> acceptHeaderElements = WebOperationContext.Current.IncomingRequest.GetAcceptHeaderElements();
            for (int x = 0; x < acceptHeaderElements.Count; x++)
            {
                string normalizedMediaType = acceptHeaderElements[x].MediaType.ToLowerInvariant();
                switch (normalizedMediaType)
                {
                    case "application/xml":
                        WebOperationContext.Current.OutgoingResponse.Format = WebMessageFormat.Xml;
                        break;
                    case "application/json":
                        WebOperationContext.Current.OutgoingResponse.Format = WebMessageFormat.Json;
                        break;
                }
            }

            return new[] { new Tram() { TramName = "Tram 1" }, new Tram() { TramName = "Tram 2" } };
        }

Now when i perform a get on the above service using Fiddler :

GET http://localhost/XMLService/multipleendpointservice.svc/pox/GetOverview HTTP/1.1
User-Agent: Fiddler
Host: localhost
Accept: application/json

My response is

HTTP/1.1 200 OK
Cache-Control: private
Content-Length: 79
Content-Type: application/json; charset=utf-8
Server: Microsoft-IIS/7.5
X-AspNet-Version: 4.0.30319
X-Powered-By: ASP.NET
Date: Wed, 30 Nov 2011 11:39:16 GMT

[{"<TramName>k__BackingField":"Tram 1"},{"<TramName>k__BackingField":"Tram 2"}]

Similarly when i perform :

GET http://localhost/XMLService/multipleendpointservice.svc/pox/GetOverview HTTP/1.1
User-Agent: Fiddler
Host: localhost
Accept: application/xml

My response is :

HTTP/1.1 200 OK
Cache-Control: private
Content-Length: 334
Content-Type: application/xml; charset=utf-8
Server: Microsoft-IIS/7.5
X-AspNet-Version: 4.0.30319
X-Powered-By: ASP.NET
Date: Wed, 30 Nov 2011 11:39:09 GMT

<ArrayOfTram xmlns="http://schemas.datacontract.org/2004/07/XMLService" xmlns:i="http://www.w3.org/2001/XMLSchema-instance"><Tram><_x003C_TramName_x003E_k__BackingField>Tram 1</_x003C_TramName_x003E_k__BackingField></Tram><Tram><_x003C_TramName_x003E_k__BackingField>Tram 2</_x003C_TramName_x003E_k__BackingField></Tram></ArrayOfTram>

NOTE: The Accept header can be other than application/xml or application/json. in such cases you need to handle it.

The other alternative is to use the WebServiceHostFactory and use the webHttpEndpoint element that has the automaticFormatSelection attribute to perform the above action