How do I determine which interface is referenced by an explicitly-implemented MethodInfo object?

Question

I have a MethodInfo object that represents an explicitly-implemented interface method, as follows.

MethodInfo GetMethod()
{
    return typeof(List<>).GetMethod(
        "System.Collections.IEnumerable.GetEnumerator",
        BindingFlags.Instance | BindingFlags.NonPublic);
}

How do I query this MethodInfo object to obtain the interface type it implements, a Type object representing System.Collections.IEnumerable? The InterfaceMapping structure provides the inverse operation, getting the MethodInfo object of a type that implements a given interface, so that won't work.

Note that this is a contrived example as I can clearly parse the method name for this information. I'd like to avoid doing this if possible.

Answer 1

I don't know of a direct way of doing this, but you can obviously use InterfaceMapping in reverse: iterate over all interfaces implemented by the method's declaring type, checking if the method is in the interface map for that interface:

foreach (Type itf in method.DeclaringType.GetInterfaces())
{
  if (method.DeclaringType.GetInterfaceMap(itf).TargetMethods.Any(m => m == method))
  {
    Console.WriteLine("match: " + itf.Name);
  }
}

Although this may seem a bit inefficient, most types implement few enough interfaces that it shouldn't be a big deal. Appreciate it's not terribly elegant though!