using System;

​

public class Program

{

     public void Test<T>()

                where T : class     // Generic Constraint   It allows only Reference types

            {

                Console.WriteLine("Hello"); // Prints Hello

            }

        public static void Main()

        {

            Program my = new Program();

            //my.Test<int>();               //it gives errorr because int is not a reference type

            my.Test<string>();

        }

}

​