I'm getting the error:

'Namespace.A' does not contain a definition for 'MyObjectInterface' and no extension method 'MyObjectInterface' accepting a first argument of type ...

I've looked at this and this and neither seems to apply.

The code looks like:

public abstract class Base
{
    public IObject MyObjectInterface { get; set; }
}

public class A : Base
{
    /**/
}

public class Implementation
{
    public void Method()
    {
        Base obj = new A();
        obj.MyObjectInterface = /* something */; // Error here
    }
}

• IObject is defined in a separate assembly, but:

  • IObject is in a separate assembly/namespace
  • Base and A are in the same assembly/namespace each with correct using directives
  • Implementation is in a third separate assembly namespace, also with correct using directives.

• Casting to A before trying to set MyObjectInterface doesn't work

• Specifically, I'm trying to set the value of MyObjectInterface to a mock object (though, I created a fake instead to no avail)

I've tried everything I can think of. Please help before I lose more hair.

edit I can't reproduce the error by creating a test app either, which is why I'm here and why I'm frustrated.

@Reed Copsey: /* something */ is either an NUnit.DynamicMock(IMailer).MockInstance or a Fake object I created that inherits from IObject and just returns canned values.

@Preet Sangha: I checked and no other assembly that is referenced has a definition for an IObject (specifically, it's called an IMailer).

Thing is that intellisense picks up the Property, but when I compile, I get CS0117. I can even 'Go To Definition' in the implementation, and it takes me to where I defined it.