static void Main(string[] args)
{
var classA1 = new ClassA1();
var classB1 = new ClassB1();
var classB2 = new ClassB2();
CallHello(classA1, "A1");
CallHello(classB1, "B1");
CallHello(classB2, "B2");
Console.WriteLine();
classA1.Hello();
Console.WriteLine();
classB1.Hello();
Console.WriteLine();
classB2.Hello();
Console.WriteLine();
Console.ReadKey();
}
