Following C#.NET demo explains you all the scenarios for implementation of Interface methods to classes. There are two ways you can implement a interface method to a class. 1. Implicit Implementation 2. Explicit Implementation. Please go though the sample.

using System;

namespace ImpExpTest

{

    class Program

    {

        static void Main(string[] args)

        {

            C o3 = new C();

            Console.WriteLine(o3.fu());

            I1 o1 = new C();

            Console.WriteLine(o1.fu());

            I2 o2 = new C();

            Console.WriteLine(o2.fu());

            var o4 = new C();       //var is considered as C

            Console.WriteLine(o4.fu());

            var o5 = (I1)new C();   //var is considered as I1

            Console.WriteLine(o5.fu());

            var o6 = (I2)new C();   //var is considered as I2

            Console.WriteLine(o6.fu());

            D o7 = new D();

            Console.WriteLine(o7.fu());

            I1 o8 = new D();

            Console.WriteLine(o8.fu());

            I2 o9 = new D();

            Console.WriteLine(o9.fu());

        }

    }

    interface I1

    {

        string fu();

    }

    interface I2

    {

        string fu();

    }

    class C : I1, I2

    {

        #region Imicitly Defined I1 Members

        public string fu()

        {

            return "Hello C";

        }

        #endregion Imicitly Defined I1 Members

        #region Explicitly Defined I1 Members

        string I1.fu()

        {

            return "Hello from I1";

        }

        #endregion Explicitly Defined I1 Members

        #region Explicitly Defined I2 Members

        string I2.fu()

        {

            return "Hello from I2";

        }

        #endregion Explicitly Defined I2 Members

    }

    class D : C

    {

        #region Imicitly Defined I1 Members

        public string fu()

        {

            return "Hello from D";

        }

        #endregion Imicitly Defined I1 Members

    }

}