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Introduction

  • Delegates are objects which point towards a method which matches its signature(values passed to the method) to that delegate.
  • Delegates are reference type used to encapsulate a method with a specific signature.
  • C++ function pointers are called as C#.NET delegates.
  • Delegates holds the address of one method or addresses of many methods.
  • Delegates hides some information like class names and method names.
  • The delegates are divided into two types, singlecast delegate and multicast delegate.
  • Single cast delegate holds the address of one method, and multicast delegate holds the addresses of many methods.
Steps for creating a delegate: 1. Write a class with a set of methods
Syntax:
class Test
{
    public void print()
    {
        logic;
    }
}
2. Create a delegate
Syntax:
Public delegate void Dname()
3. Create an object for the delegate with the address of a method
Syntax:
Test t=new Test();
Dname x=new Dname(t.print);
4. Call the delegate object--> x();
Example on single cast delegates: Open windows forms application project
Place a button
Code in general declaration
class Test
{
    public void print()
    {
    MessageBox.Show("from print");
    }//print
    }//test
    public delegate void XYZ();
    private void button1_Click(object sender, EventArgs e)
    {
        Test t = new Test();
        XYZ x = new XYZ(t.print);
        x();
}

Working with Multicast Delegate:

  • Multicast delegate holds a collection of methods.
  • Multicast delegate holds a sequence of methods.
  • A collection of single cast delegates is also called as Multicast delegate.
  • Multicast delegate supports arithmetic + and - operations.
  • + operator adds a method into the sequence.
  • - operator remove a method from the sequence.

Example on Multicast delegate:

Open console application project.
Code in general declaration(Before main method).
class program
{
        class Test
        {
            public void m1()
            {
                Console.Write("GM");
            }//m1
            public void m2()
            {
                Console.WriteLine("GA");
            }//m2
        }//test
    }//program
    public delegate void Dname();
        
static void Main()
{
    Test t = new Test();
    Dname d1, d2, d3, d4, d5, d6;
    d1 = new Dname(t.m1);
    d2 = new Dname(t.m2);
    d3 = d1 + d2;
    Console.WriteLine("from D3");
    D3();
    D4 = D3 + D3;
    Console.WriteLine("from D4");
    D4();
    D5 = D4 - D1;
    Console.WriteLine("from D5");
    D5();
    D6 = D5 - D3 - D2;
    Console.WriteLine("from D6");
    D6();//Null reference
    Console.ReadKey();
}

Comments/Suggestions are invited. Happy coding......!

Comments Post a Comment

Sacrates.Jebamalai 2/10/2013 (IST) / Reply

Very useful for me...thanks Renuka