Unable to cast object of type MyObject to type MyObject

Question

I have this scenario where a webservice method I'm consuming in C# returns a Business object, when calling the webservice method with the following code I get the exception "Unable to cast object of type ContactInfo to type ContactInfo" in the reference.cs class of the web reference

Code:

ContactInfo contactInfo = new ContactInfo();
Contact contact = new Contact();

contactInfo = contact.Load(this.ContactID.Value);

Any help would be much appreciated.

Answer 1

This is because one of the ContactInfo objects is a web service proxy, and is in a different namespace.

It's a known problem with asmx-style web services. In the past I've implemented automatic shallow-copy to work around it (here's how, although if I were doing it again I'd probably look at AutoMapper instead).

For example, if you have an assembly with the following class:

MyProject.ContactInfo

and you return an instance of it from a web method:

public class DoSomethingService : System.Web.Services.WebService
{
    public MyProject.ContactInfo GetContactInfo(int id)
    {
        // Code here...
    }
}

Then when you add the web reference to your client project, you actually get this:

MyClientProject.DoSomethingService.ContactInfo

This means that if, in your client application, you call the web service to get a ContactInfo, you have this situation:

namespace MyClientProject
{
    public class MyClientClass
    {
        public void AskWebServiceForContactInfo()
        {
            using (var service = new DoSomethingService())
            {
                MyClientProject.DoSomethingService.ContactInfo contactInfo = service.GetContactInfo(1);

                // ERROR: You can't cast this:
                MyProject.ContactInfo localContactInfo = contactInfo;
            }
        }
    }
}

It's on that last line that I use my ShallowCopy class:

namespace MyClientProject
{
    public class MyClientClass
    {
        public void AskWebServiceForContactInfo()
        {
            using (var service = new DoSomethingService())
            {
                MyClientProject.DoSomethingService.ContactInfo contactInfo = service.GetContactInfo(1);

                // We actually get a new object here, of the correct namespace
                MyProject.ContactInfo localContactInfo = ShallowCopy.Copy<MyClientProject.DoSomethingService.ContactInfo, MyProject.ContactInfo>(contactInfo);
            }
        }
    }
}

NOTE
This only works because the proxy class and the "real" class have exactly the same properties (one is generated from the other by Visual Studio).