Delegates in C#

Delegates – It is a type that holds the reference of method in an object. It’s also called type safe (It ensure that operation is working on right kind of data) function pointer.

Adv –    Encapsulating the method call from caller

                Effective use of delegate improve the performance

                Use to call method asynchronously.

                Declare Delegate ->Public Delegate int delegate_name(Param optional)

                Multicast Delegate – holds the reference of more than one method. Must contain the methods return void.

How to use

                Single Delegate

 private  delegate void d_Print(string strPrint);

        private delegate int d_Add(int fNum, int sNum);

        static void Main(string[] args)

        {

            //Simple Use of Delegate

            d_Print print = PrintString;

            print("Hello");

            //Pass Delegate as parameter

            PrintHelper(PrintString, "Hello");

            //Delegate With return value

            d_Add add = AddTwoNumbers;

            Console.Write(add(4, 5));

        }

        private static void PrintString(string strPrint)

        {

            Console.Write(strPrint);

        }

        //Pass delegate as parameter

        private static void PrintHelper(d_Print dP, string strPrint)

        {

            dP(strPrint);

        }

        //Add two numbers

        private static int AddTwoNumbers(int num1, int num2)

        { return num1 + num2; }

Multicast Delegate

 private delegate int d_ArithmeticOpr(int fNum, int sNum);

        static void Main(string[] args)

        {

            //Use of multicast Delegate

            d_ArithmeticOpr math = new d_ArithmeticOpr(AddTwoNumbers);

            //Add Subtract Method to delegate object

            math += new d_ArithmeticOpr(SubtractNumber);

            //This call will do both Addition and Subtraction

            Console.Write(math(20, 10));

            //remove Add call from delegate

            math -= new d_ArithmeticOpr(AddTwoNumbers);

            //This call only do the Subtraction

            Console.Write(math(20, 10));

        }

        //Subtract Two Numbers

        private static int SubtractNumber(int num1, int num2)

        {

            return (num1-num2);

        }

        //Add two numbers

        private static int AddTwoNumbers(int num1, int num2)

        { return num1 + num2; }