ASMX not generating WSDL when using Custom IHttpHandlerFactory

Question

I am implementing a dynamic ASMX web service via a custom HttpHandler, and my web service has recently stopped generating WSDL automatically. When I use ?WSDL on the asmx url, I get the following error:

System.InvalidOperationException: XML Web service description was not found.
   at System.Web.Services.Protocols.DiscoveryServerProtocol.WriteReturns(Object[] returnValues, Stream outputStream)
   at System.Web.Services.Protocols.WebServiceHandler.WriteReturns(Object[] returnValues)
   at System.Web.Services.Protocols.WebServiceHandler.Invoke()

This worked fine a while ago, so I'm wondering if there's a file permission problem somewhere.

A Google search does not return any reference to this particular situation.

I doubt that my code is relevant to the problem; it has not changed:

[WebService(Description = "...", Namespace = "...")]
[WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
[ToolboxItem(false)]
public class MyWebService : System.Web.Services.WebService
{
    [WebMethod]
    void MyWebMethod() {}
}

public class VirtualWebServiceFactory : IHttpHandlerFactory
{
    public IHttpHandler GetHandler(HttpContext context, string requestType, string url, string pathTranslated)
    {
        WebServiceHandlerFactory wshf = new WebServiceHandlerFactory();
        MethodInfo coreGetHandler = wshf.GetType().GetMethod("CoreGetHandler", BindingFlags.NonPublic | BindingFlags.Instance);
        IHttpHandler handler = (IHttpHandler)coreGetHandler.Invoke(wshf, new object[] { typeof(MyWebService), context, context.Request, context.Response });    
        return handler;
    }
}

Decompiling System.Web.Services.Protocols.DiscoveryServerProtocol.WriteReturns() reveals that it looks up the XML service description in a dictionary created somewhere else.

I was hoping that someone familiar with the DiscoverServerProtocol etc. might know under what circumstances the XML service description might fail to be built.

The following works just fine:

ServiceDescriptionReflector reflector = new ServiceDescriptionReflector();
reflector.Reflect(typeof(MyWebService), "...");

Navigating to MyWebService.asmx shows all the functions and allows testing them. But using ?WSDL gives the exception above.

Answer 1

Just for fun, try making your WebMethod public.

However, the real answer is to not screw around with .NET Framework code that's not meant to be called. What's wrong with just calling GetHandler? What are you trying to accomplish here that can't be accomplished without messing around in the internals of an obscure class?

Answer 2

Hmm, after many months, found out that the URL was being re-written to include other parameters than the ?WSDL, which made the private function choke.