Scenario :-

Private Implementation of Interface member.
Remember OOPS is a bit tricky and if you write MyClass definition as below then

    public interface MyInterface1
    {
        int foo();
    }

    public class MyClass : myinterfacse
    {
     int a=10;
     int foo()
      {
       return a;
      }
    }

It will give a compile time error.
Error 1 ‘WindowsFormsApplication3.Program.MyClass’ does not implement interface member ‘WindowsFormsApplication3.Program.myinterfacse.foo()’. ‘WindowsFormsApplication3.Program.MyClass.foo()’ cannot implement an interface member because it is not public.