WCF DataContractSerializer doesn't pick up contract attributes... why not?

Question

I have the following type which I use as a message contract in WCF:

[MessageContract(IsWrapped = true, 
                 WrapperNamespace = "http://example.com/services", 
                 WrapperName = "EchoRequest")]
public class EchoRequest
{
    public EchoRequest() { }
    public EchoRequest(String value)
    {
        Value = value;
    }

    [MessageBodyMember(Name = "Value", 
                       Namespace = "http://example.com/services", 
                       Order = 0)]
    public String Value { get; set; }
}

When I generate a proxy to this type using svcutil.exe, I get a client which is able to communicate to a service which hosts it, with the XML namespaces on the elements correct according to the Message Contract attributes.

When I use Message.CreateMessage(...) on an instance of it, the namespaces revert to the default (http://schemas.datacontract.org/2004/07/...). When I use an instance of DataContractSerializer, the same thing happens. I try to pass a namespace to the DataContractSerializer constructor, and only the wrapper gets included in the namespace:

var requestMessage = new EchoRequest("hello, world!");
var serializer = new DataContractSerializer(typeof(EchoRequest), 
                                            "EchoRequest", 
                                            "http://example.com/services");
var stream = new MemoryStream();
serializer.WriteObject(stream, requestMessage);
var data = Encoding.UTF8.GetString(stream.ToArray());

At this, "data" is:

<EchoRequest xmlns="http://example.com/services"
             xmlns:a="http://schemas.datacontract.org/2004/07/TestClient"
             xmlns:i="http://www.w3.org/2001/XMLSchema-instance">
    <a:Value>hello, world!</a:Value>
</EchoRequest>

Why does the DataContractSerializer appear to ignore the MessageContract attributes? How does svcutil get this work?

Answer 1

It's because message contracts are not data contracts, data contracts use different attributes to mark their classes. Try using a typed message converter;

EchoRequest echoRequest = new EchoRequest{ value = "Hello" };

TypedMessageConverter echoMessageConverter = TypedMessageConverter.Create(
                 typeof(echoRequest),
                 "YourActionNameHere",
                 "http://example.com/services");
Message request = echoMessageConverter.ToMessage(
    echoRequest,MessageVersion.Soap11);

You'll then have a message all ready to go and can pull the request body out if you need to.