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
    }
}

Output:-

Hello C
Hello from I1
Hello from I2
Hello C
Hello from I1
Hello from I2
Hello from D
Hello from I1
Hello from I2