Question

I’m trying to create a generic WCF service invoker utility but my knowledge of generics, delegates and lambda is failing me at the final hurdle.

I want to be able to encapsulate the authentication and expection handling of calling my WCF web services so that I can consume the web service with just the Interface, request and response classes to hand.

I don’t understand how I can pass in the method name I want to execute – I have tried the Func<> route but am getting confused as I get a recursion error with what I have implemented below. I would prefer to not go down the hard coded string / reflection route either – I want this to be a strongly-typed class.

Please help!

Thank you

public static TResponse Invoke<TService, TRequest, TResponse>(TRequest request, Func<TService, TRequest, TResponse> methodToExecute, string endpointConfigurationName) where TResponse : class
{
  ChannelFactory<TService> channel = new ChannelFactory<TService>(endpointConfigurationName);

  // attach auth credentials
  channel.Credentials.UserName.UserName = "myUserName";
  channel.Credentials.UserName.Password = "myPassword";

  // create a proxy for the channel
  TService proxy = channel.CreateChannel();
  TResponse response;

  try
  {
    response = methodToExecute(proxy, request);
    channel.Close();
  }
  catch
  {
    // abort or close in a fail-safe manner
      if (channel.State == CommunicationState.Faulted)
      {
        channel.Abort();
      }
      else
      {
        channel.Close();
      }

      throw;
  }

  return response;
}

Answer 1

Here’s my try. My version doesn’t have the request type as a parameter. I show how I expect you to use it (you didn’t show how you planned to invoke yours, but I suspect that the problem was in the invocation, not the method itself).

    private class Response {}

    private interface IService
    {
        Response MyMethod(object i); 
    }

    public static void Foo()
    {
        object request = 1;
        Response response = Invoke((IService service) => service.MyMethod(request), "endpoint");
    }

    public static TResponse Invoke<TService, TResponse>(Func<TService, TResponse> methodToExecute, string endpointConfigurationName) where TResponse : class
    {
        ChannelFactory<TService> channel = new ChannelFactory<TService>(endpointConfigurationName);

        // attach auth credentials
        channel.Credentials.UserName.UserName = "myUserName";
        channel.Credentials.UserName.Password = "myPassword";

        // create a proxy for the channel
        TService proxy = channel.CreateChannel();
        TResponse response;

        try
        {
            response = methodToExecute(proxy);
            channel.Close();
        }
        catch
        {
            // abort or close in a fail-safe manner
            if (channel.State == CommunicationState.Faulted)
            {
                channel.Abort();
            }
            else
            {
                channel.Close();
            }

            throw;
        }

        return response;
    }