Method 'XYZ' cannot be reflected

Question

We have consumed a third party web service and are trying to invoke it from an ASP.NET web application. However when I instantiate the web service the following System.Inval

Answer 1

Another scenario where this error can happen: I simply had another web method with the same name (but different parameters)in my web service that slipped in during a code merge. After I deleted the old method it worked.