static void Main() { Customer C1 = new Customer(); C1.Customer2Print(); C1.Customer3Print(); C1.Customer1Print(); ICustomer2 IC2 = new Customer(); IC2.Customer2Print(); // Only ICustomer2 member available. Program P = new Program(); ((I1)P).InterfaceMethod(); //As the method names in both the interface us same. InterfaceMethod() cannot be called on Program object. ((I2)P).InterfaceMethod(); /* OR */ I1 i1 = new Program(); I2 i2 = new Program(); i1.InterfaceMethod(); i2.InterfaceMethod(); /* OR */ I1 ii1 = new Program(); I2 ii2 = (Program)ii1; //may not be a good practice in actual, but depends. ii1.InterfaceMethod(); ii2.InterfaceMethod(); Console.ReadKey(); }