Today, in this article we will dig out and play around by creating simple
delegate program and let's see how better we can perform in this single program
only. I mean, in this program I will cover everything all stuff required for
delegate from all the possible ways. So I will be covering simple delegate
creation, multi-cast delegate, use of named methods, use of anonymous methods,
use of lambda expression and finally much better implementation about all of
these and generic delegates as well.
What are Delegates?
Definition:
Delegate is an object which cross references the method which you want to
actually point and fire. The method signature must match with delegate variable
parameters declaration. It's Type Safe.
Question Arises: When To This Stuff????
- You would use when you want to pass on some anonymous methods.
- You would use when you want to chain multiple methods using single operated action.
- You would use when you don't have to create an extra methods. To get rid of over headed methods with usage simple lambda expressions.\
- You would use when you are very eager to easy combination and follow design patterns.
- You would use when you eager to differentiate declarations and implementations.
Types of Delegates:
- Single Cast Delegate:
This type is one that fires off single method which has same signatures.
- Multi Cast Delegate:
This type is one that fires off multiple methods which has same signatures.
What are Named Methods?
The Delegates which are interrelated with some predefined methods in our
application. Which are assigned to delegate variable are called as Named
Methods.
VijayDelegates<int,
int> p = new
VijayDelegates<int, int>(b.Add);
int
result = p(22, 20);
Response.Write("<center><b><i><h1>" + result
+ "</h1></i></b></center>");
What are Anonymous Methods?
We can simple say that these methods are that which does not have any specific
name but indeed performs an expected operation by passing itself as a value
parameter to delegate.
VijayDelegates<int,
int> p;
p = delegate(int
r1, int r2)
{
return r1 * r2;
};
int result = p(34, 3);
Response.Write("<center><b><i><h1>" + result
+ "</h1></i></b></center>");
What is Lambda Expression?
Lambda Expression holds block of Code with expression and statements which
performs an expected operation without creating much over head with lambda
operator where it goes and fetches the data by overlooking towards anonymous
methods.
VijayDelegates<int,
int> p;
p = (x, y) => x / y;
int
result = p(500, 20);
Response.Write("<center><b><i><h1>" + result
+ "</h1></i></b></center>");
What is GenericDelegate?
It accepts data in the delegate variable to be user-defined which enables to
easily type cast the intended data. It is denoted by Type <T>.
public delegate int
VijayDelegates<T1, T2>(T1 var1, T2 var2);
Now, we don't like to waste much more time on studying the theory. It's Time for
us to get started with delegates.
For all this concepts implementation and demonstration I will be now creating
simple webform in 4.0 with C#. I have created four buttons and added simple CSS
to enhance the Look and Feel of Application. I have performed the delegate
operations in code behind file.
The Complete Source Code for WebForm1.aspx looks like this:
<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="WebForm1.aspx.cs" Inherits="Simple_Delegates_Web_Application.WebForm1" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head id="Head1" runat="server">
<title></title>
<style type="text/css">
.class
{
font-style:
oblique;
color:
#800000;
font-family:
Cambria;
font-size:
large;
font-weight:
bold
}
</style>
</head>
<body>
<form id="form1" runat="server">
<div>
<center>
<asp:Button ID="Button1" runat="server" Text="Addition" Width="107px"
onclick="Button1_Click" CssClass="class" />
<br />
<br />
<asp:Button ID="Button2" runat="server" Text="Substraction"
onclick="Button2_Click" CssClass="class"/>
<br />
<br />
<asp:Button ID="Button3" runat="server" Text="Multiply" Width="105px"
onclick="Button3_Click" CssClass="class"/>
<br />
<br />
<asp:Button ID="Button4" runat="server" Text="Division" Width="105px"
onclick="Button4_Click" CssClass="class"/>
<br />
<br />
</center>
</div>
</form>
</body>
</html>
The Complete Source Code for Class1.cs looks like this:
using
System;
using
System.Collections.Generic;
using
System.Linq;
using System.Web;
using
System.Web.UI.WebControls;
namespace
Simple_Delegates_Web_Application
{
public class Class1
{
public int
Add(int x, int
y)
{
return x + y;
}
public int
Sub(int x, int
y)
{
return x - y;
}
}
}
The Complete Source Code for WebForm1.aspx.cs looks like this:
using
System;
using
System.Collections.Generic;
using
System.Linq;
using System.Web;
using
System.Web.UI;
using
System.Web.UI.WebControls;
namespace
Simple_Delegates_Web_Application
{
public partial class WebForm1
: System.Web.UI.Page
{
public delegate int VijayDelegates<T1,
T2>(T1 var1, T2 var2);
protected void
Page_Load(object sender,
EventArgs e)
{
}
Class1 b = new Class1();
protected void
Button1_Click(object sender,
EventArgs e)
{
VijayDelegates<int,
int> p = new VijayDelegates<int,
int>(b.Add);
int result = p(22, 20);
Response.Write("<center><b><i><h1>"
+ result + "</h1></i></b></center>");
}
protected void
Button2_Click(object sender,
EventArgs e)
{
VijayDelegates<int,
int> p = new VijayDelegates<int,
int>(b.Sub);
int result = p(30, 20);
Response.Write("<center><b><i><h1>"
+ result + "</h1></i></b></center>");
}
protected void
Button3_Click(object sender,
EventArgs e)
{
VijayDelegates<int,
int> p;
p = delegate(int
r1, int r2)
{
return r1 * r2;
};
int result = p(34, 3);
Response.Write("<center><b><i><h1>"
+ result + "</h1></i></b></center>");
}
protected void Button4_Click(object
sender, EventArgs e)
{
VijayDelegates<int,
int> p;
p = (x, y) => x / y;
int result = p(500, 20);
Response.Write("<center><b><i><h1>"
+ result + "</h1></i></b></center>");
}
}
}
Output of This Program looks like this:
- For Addition Part:
- For Multiplication Part:
- For Subtraction Part:
I hope this article is useful for you....