Working With Delegates in C#

INTRODUCTION

Delegates are function pointers. Delegates can be chained together; for example, multiple methods can be called on a single event. There are two types of delegates.

• Single Cast Delegate

• Multi Cast Delegates

A Singlecast delegate can return any datatype and contain the address of one function. It is derived from the System.Delegate class. It contains the reference of one method at a time. A Multicast delegate does not return any value and contains addresses of multiple functions. It is derived from the System.MulticastDelegate class.

The foillowing steps are used to create delegates.

Step 1: Open Visual Studio 2010 and click on file->new->project->and click console application.

Step 2: Write the following code for a Singlecast delegate.

namespace ConsoleApplication2

{

class Program

{

static void Main(string[] args)

{

singlecast ob = new singlecast(abc.mul);//delegate instantiation

int a = ob(4, 2);

Console.WriteLine("The multiplication is"+a);

ob = new singlecast(abc.add);

int b = ob(10, 2);

Console.WriteLine("The addition is:" + b);

ob = new singlecast(abc1.div);

int c = ob(6, 3);

Console.WriteLine("The division is:"+b);

}

}

delegate int singlecast(int x, int y); //Delegate declaration

class abc

{

internal static int add(int a,int b)//return type should be match with the delegate return type.and same number of arguments as in the delegates.

{

return a+b;

}

internal static int mul(int a,int b)

{

return a*b;

}

}

class abc1

{

internal static int div(int a,int b)

{

return a/b;

}

}

}

Step 3: Now to run the program by pressing Ctrl+F5, and the output is as:

Step 4: Add the following code for a multicast delegate:

delegate void Notifier(int i,int j); //declare delegate

class calculation

{

public void add(int a, int b) //method declaration

{

Console.WriteLine("Addition is " + (a + b));

}

public void substraction(int x, int y)

{

Console.WriteLine("substraction is " + (x - y));

}

}

class MTest

{

public static void Main()

{

calculation obj = new calculation();

Notifier number;

number = new Notifier(obj.add);

number += new Notifier(obj.substraction);

number(10, 2);

number -= new Notifier(obj.substraction);

number(4, 2);

Console.ReadLine();

}

}

Step 5: Run the application by pressing F5 and the output is as:

Summary: In this article I explain the singlecast delegate and the multicast delegate. I hope this will be helpful for you.