Shaohen’s C# Documentation

To determine whether an object is of a certain type: we can use the is operator. It will return a boolean result.

expr is type

Returns true if the expression object is of type type or has it derived from type, else it will return false.

This is an example:

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("Never will be displayed");
        else
            Console.WriteLine("a is not a B");

        if (b is B)
            Console.WriteLine("b is a B");
        if (a is object)
            Console.WriteLine("a is an Object");

        }
    }

(Taken from C#: The Complete Reference from Herbert Schildt).

The result is
a is an A
b is an A because it is derived from A
a is not a B
b is a B
a is an Object