How to call an explicitly implemented interface-method on the base class

Question

I have a situation, where two classes (one deriving from the other) both implement the same interface explicitly:

interface I
{
  int M();
}

class A : I
{
          


        

Answer 1

it is necessary explicitly?... Can you use an abstract class or class instead of interface?

interface ISample {}
class A : ISample {}
class B : A {}
...
base.fun();
...

http://msdn.microsoft.com/en-us/library/hfw7t1ce(v=vs.71).aspx

I have no idea its not possible call base method when it comes from implementation of interface.