how to create a message from scracth?

Question

Hello,

I'm writing a MessageEncoder because I'm receiving a non-standard stream and I want to create a message from it's values, so:

1) I 'understand' the parameters of the operation from the stream and use a DataContractSerializer to serialize them to the body of the message...

The question is:

How do I correctly write the body of the message??? Because I can write a parameter using the DCS but I can't write the Operation Name, so the dispatcher fails when it tries to resolve the call:

OperationFormatter encountered an invalid Message body. Expected to find node type 'Element' with name '[OperationContract_Name]' and namespace '[ServiceContract_Namespace]'. Found node type 'Element' with name '[DataContract_Name]' and namespace '[DataContract_Namespace]'

This is: I'm sending the parameter of the operation contract that I want to call, but I don't write the first element with the operation contract name...

So, how can I do that???

 

Thanks,

M

 

 

 

 

Answer 1

Your best bet is probably find some auto-generated message and model from there.  We generally don't support handcrafted messages since anything could go wrong in there.  I am afraid no one here could answer your question with a simple paragraph...

Answer 2

If you want to know exactly what's the expected format of the body of the message, you can add an inspector to your service, call it from a WCF client, and see what the message looks like. The code below shows how it can be done for a simple service.

[ServiceContract]
public interface ITest1201739
{
    [OperationContract]
    int Add(int x, int y);
}
public class Service1201739 : ITest1201739
{
    public int Add(int x, int y) { return x + y; }
}
public class MyEndpointBehavior : IEndpointBehavior
{
    public void AddBindingParameters(ServiceEndpoint endpoint, BindingParameterCollection bindingParameters) { }
    public void ApplyClientBehavior(ServiceEndpoint endpoint, ClientRuntime clientRuntime) { }
    public void ApplyDispatchBehavior(ServiceEndpoint endpoint, EndpointDispatcher endpointDispatcher)
    {
        endpointDispatcher.DispatchRuntime.MessageInspectors.Add(new MyMessageInspector());
    }
    public void Validate(ServiceEndpoint endpoint) { }
}
public class MyMessageInspector : IDispatchMessageInspector
{
    public object AfterReceiveRequest(ref Message request, IClientChannel channel, InstanceContext instanceContext)
    {
        MessageBuffer buffer = request.CreateBufferedCopy(int.MaxValue);
        Message temp = buffer.CreateMessage();
        Console.WriteLine("Message envelope: " + temp);
        XmlWriterSettings writerSettings = new XmlWriterSettings();
        writerSettings.Indent = true;
        writerSettings.IndentChars = " ";
        writerSettings.OmitXmlDeclaration = true;
        XmlWriter writer = XmlWriter.Create(Console.Out, writerSettings);
        Console.WriteLine("Message body:");
        writer.WriteNode(temp.GetReaderAtBodyContents(), true);
        writer.Flush();
        request = buffer.CreateMessage();
        return null;
    }
    public void BeforeSendReply(ref Message reply, object correlationState) { }
}
public class Test1201739
{
    public static void Run()
    {
        ServiceHost host = new ServiceHost(typeof(Service1201739));
        string address = http://localhost:8000/Service1201739;
        BasicHttpBinding binding = new BasicHttpBinding();
        host.AddServiceEndpoint(typeof(ITest1201739), binding, address).Behaviors.Add(new MyEndpointBehavior());
        host.Open();
        ChannelFactory<ITest1201739> factory = new ChannelFactory<ITest1201739>(binding, new EndpointAddress(address));
        ITest1201739 proxy = factory.CreateChannel();
        Console.WriteLine(proxy.Add(123, 456));
        ((IChannel)proxy).Close();
        factory.Close();
        host.Close();
    }
}

For this contract/binding, the expected format of the message body is the following ("http://tempuri.org" is the default namespace of the contract)

<Add xmlns="http://tempuri.org/">
  <x>123</x>
  <y>456</y>
</Add>

As long as you follow the same format, the message should be accepted by the formatter.