Is Operator in C# with Example

From inheritance, we know that a base class always contains most of the common features and we also know a base class reference variable can point to the derived class object, but vice versa is not possible because a derived class is an extended version of a base class and it contains more functionally than a base class.  Due to this reason, we can easily point a derived class object to a base class reference variable using type casting, but vice versa is not possible because there will be a run time error.

using System;

namespace Hello
{   
    //Employee Class
     class Employee
    {
        public void PrintName()
        {
            Console.WriteLine("This is an Employee Class.");
        }

    }

    //Manager Class
    class Manager:Employee
    {
        public new void PrintName()
        {
            Console.WriteLine("This is a Manager Class.");
        }

    }

    class Program
    {
        static void Main(string[] args)
        {
            Manager man = new Manager();

            //Type casting
            Employee emp = (Employee)man;

            emp.PrintName();
        }
            
    }
}

 Output:

This is an Employee Class.
Press any key to continue . . .

There is always is-a relationship between between base class and derived class.  For example, consider there is a base class called Employee.  You have 2 more classes, called Manager and Supervisor, which are inheriting from Employee base class.  By the concept of is-a relationship, Manager is-a Employee and Supervisor is-a Employee.  Every Employee cannot be Manager or Supervisor.

While type casting, there are chances that you will encounter run time error and to overcome this issue, we always check for is-relationship.  To find this is-a relationship, we use is operator, which returns a boolean value (true or false).  Using is operator, you can check whether an underlying class of the object is inheriting from other class or not.

using System;

namespace Hello
{   
    //Employee Class
     class Employee
    {
        public void PrintName()
        {
            Console.WriteLine("This is an Employee Class.");
        }

    }

    //Manager Class
    class Manager:Employee
    {
        public new void PrintName()
        {
            Console.WriteLine("This is a Manager Class.");
        }

    }

    class Program
    {
        static void Main(string[] args)
        {
            Manager man = new Manager();

            //This is-a relationship check
          if(man is Employee)
          {
              Employee emp = (Employee)man;
              emp.PrintName();
          }          

           
        }
            
    }
}

 Output:

This is an Employee Class.
Press any key to continue . . .

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