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

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.