How to avoid 'Method is never used' message?

Question

In the following example, Resharper complains about DoA() method never being used, despite being implemented by the 'AImplementator' class:

namespace Test
{
    public interface A
    {
        // Method 'DoA' is never used
        void DoA();
    }

    public class AImplementator: A
    {
        public void DoA()
        {
            throw new System.NotImplementedException();
        }
    }
}

I can't understand this behavior, since the interface IS being used.

1. Why this happens?
2. How can I fix this warning?

Obs: I can supress the warning using comments or the [UsedImplicitly] attribute. But neither of these options seems to be correct given the situation. I'm using Resharper 9.1.

Answer 1

This warning will only be displayed when the Solution-Wide Analysis is enabled.

The warning is about the usage (in this case e.g. a call) of the interface method. The following example should demonstrate it (note the var vs. interface as local variable type).

var instance = new AImplementator();
// Does NOT make A.DoA() "used":
instance.DoA();

A instanceAsInterface = new AImplementator();
// DOES make A.DoA() "used":
instanceAsInterface.DoA();