Using is

//listing 1
// Demonstrate is.
//complete reference chapter 17
//csc typeof_is.cs
using System;
class A {}
class B : A {}
class UseIs {
public static void Main() {
A a = new A();
B b = new B();
if(a is A) Console.WriteLine("a is an A");
if(b is A)
Console.WriteLine("b is an A because it is derived from A");
if(a is B)
Console.WriteLine("This won't display -- a not derived from B");
if(b is B) Console.WriteLine("B is a B");
if(a is object) Console.WriteLine("a is an Object");
}
}