Accessing asmx WebService Using WCF

Question

I am trying to access an old ASMX webservice using WCF by calling the ChannelFactory.CreateChannel() method.

If the web service is created by WCF, everything is straightforward. I can instantiate the proxy client generated by the svcutil tool, or manually call the ChannelFactory.CreateChannel() method. Afterwards, I can call the web service methods the same way for both scenarios.

But if the web service is of the old ASMX variety, I can still instantiate the proxy either way, but I am unable to call the same web service method.

For example, assume this basic WCF web service interface:

[ServiceContract]
public interface IWebService
{
    [OperationContract]
    string HelloWorld();
}

After using svcutil to generate the proxy, I can call HelloWorld() one of 2 ways:

WebServiceClient proxy = new ServiceReference.WebServiceClient();
textBox1.Text += proxy.HelloWorld();

or:

ChannelFactory<ServiceReference.IWebService2> cfactory = 
    new ChannelFactory<ServiceReference.IWebService>("BasicHttpBinding_IWebService");
ServiceReference.IWebService proxy = cfactory.CreateChannel();
((IClientChannel)proxy).Open();
textBox1.Text += proxy.HelloWorld();

Now assume this ASMX web service:

[WebService(Namespace = "http://tempuri.org/")]
[WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
public class WebService : System.Web.Services.WebService
{
    public WebService() {   }

    [WebMethod]
    public string HelloWorld()
    {
        return "Hello World";
    }
}

Calling HelloWorld() using the SoapClient generated by svcutil tool is nearly the same as if it were a WCF web service:

WebServiceSoapClient proxy = new ServiceReference.WebServiceSoapClient();
textBox1.Text += proxy.HelloWorld();

But trying to call HelloWorld() if you create the channel yourself and you will get an error:

ChannelFactory<ServiceReference.WebServiceSoap> cfactory =
     new ChannelFactory<ServiceReference.WebServiceSoap>("WebServiceSoap");
ServiceReference.WebServiceSoap proxy = cfactory.CreateChannel();
((IClientChannel)proxy).Open();
textBox1.Text += proxy.HelloWorld();

The error is "No overload for method HelloWorld takes 0 arguments".

It appears it is because the HelloWorld method in the autogenerated interface (ServiceReference.WebServiceSoap) takes an argument of type ServiceReference.HelloWorldRequest.

So in the end, I was only able to make it work by looking through the svcutil generated code and change my implementation to this:

ChannelFactory<ServiceReference.WebServiceSoap> cfactory = 
    new ChannelFactory<ServiceReference.WebServiceSoap>("WebServiceSoap");
ServiceReference.WebServiceSoap proxy = cfactory.CreateChannel();
((IClientChannel)proxy).Open();
ServiceReference.HelloWorldRequest inValue = 
    new WCFConsumeWebServices.ServiceReference.HelloWorldRequest();
inValue.Body = new WCFConsumeWebServices.ServiceReference.HelloWorldRequestBody();
ServiceReference.HelloWorldResponse retVal = proxy.HelloWorld(inValue);
textBox1.Text += retVal.Body.HelloWorldResult;

Is this how it is suppose to be?

For one type of basic http web service, we get to use virtually the same code to call a method, but for another we need to muck through the generated proxy code and have different implementation depending on how you open the channel ?

Answer 1

Offhand, I don't know why, but WCF appears to be using a Message Contract when it talks to your ASMX service. Have you posted the entire service?