Combine Delegates in C#

Introduction

This article demonstrates one of interesting and most useful concept in C#.

Question: What is combine delegates?

In simple terms "It is the process of combining multiple methods to assign to single delegate object".

Step 1: Create a new web application

Step 2: The complete code of webform1.aspx looks as below

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="WebForm1.aspx.cs" Inherits="CombineDelegatesApp.WebForm1" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

</head>

<body>

<div>

<table>

<tr>

<asp:Label ID="Label1" runat="server" Text="Combine Delegates" Font-Bold="true" Font-Size="Large"

Font-Names="Verdana" ForeColor="Maroon"></asp:Label>

</td>

</tr>

<tr>

<td>

<asp:Label ID="Label6" runat="server" Text="Please Enter FirstNumber" Font-Size="Large"

Font-Names="Verdana" Font-Italic="true"></asp:Label>

</td>

<td>

<asp:TextBox ID="TextBox4" runat="server"></asp:TextBox>

</td>

</tr>

<tr>

<td>

<asp:Label ID="Label2" runat="server" Text="Please Enter SecondNumber" Font-Size="Large"

Font-Names="Verdana" Font-Italic="true"></asp:Label>

</td>

<td>

<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>

</td>

</tr>

<tr>

<asp:Button ID="Button1" runat="server" Text="Addition" Font-Names="Verdana" Width="213px"

BackColor="Orange" Font-Bold="True" OnClick="Button1_Click" />

</td>

</tr>

<tr>

<asp:Button ID="Button2" runat="server" Text="Substraction" Font-Names="Verdana"

Width="213px" BackColor="Orange" Font-Bold="True" OnClick="Button2_Click" />

</td>

</tr>

<tr>

<asp:Button ID="Button3" runat="server" Text="Multiplication" Font-Names="Verdana"

Width="213px" BackColor="Orange" Font-Bold="True" OnClick="Button3_Click" />

</td>

</tr>

<tr>

<asp:Button ID="Button4" runat="server" Text="Division" Font-Names="Verdana" Width="213px"

BackColor="Orange" Font-Bold="True" OnClick="Button4_Click" />

</td>

</tr>

<tr>

<asp:Label ID="Label5" runat="server" Font-Bold="true" Font-Names="Verdana"></asp:Label>

</td>

</tr>

</table>

</div>

</center>

</form>

</body>

</html>

Step 3: The complete code of webform1.aspx.cs looks as below

using System;

using System.Collections.Generic;

using System.Linq;

using System.Web;

using System.Web.UI;

using System.Web.UI.WebControls;

namespace CombineDelegatesApp

{

public partial class WebForm1 : System.Web.UI.Page

{

protected void Page_Load(object sender, EventArgs e)

{

}

public delegate double Arthmetic(double a, double b);

protected void Button1_Click(object sender, EventArgs e)

{

if (string.IsNullOrEmpty(TextBox4.Text) || string.IsNullOrEmpty(TextBox1.Text))

{

Label5.Text = "Please Enter Some Values"; Label5.ForeColor = System.Drawing.Color.Red;

}

else

{

Arthmetic result = GetAddResult();

Label5.Text = String.Format("Addition Result is: {0}", result(double.Parse(TextBox4.Text), double.Parse(TextBox1.Text)));

Label5.ForeColor = System.Drawing.Color.Green; TextBox4.Text = string.Empty;

TextBox1.Text = string.Empty;

}

protected void Button2_Click(object sender, EventArgs e)

{

if (string.IsNullOrEmpty(TextBox4.Text) || string.IsNullOrEmpty(TextBox1.Text))

{

Label5.Text = "Please Enter Some Values"; Label5.ForeColor = System.Drawing.Color.Red;

}

else

{

Arthmetic result = GetSubResult();

Label5.Text = String.Format("Substraction Result is: {0}", result(double.Parse(TextBox4.Text), double.Parse(TextBox1.Text)));

Label5.ForeColor = System.Drawing.Color.Green;

TextBox4.Text = string.Empty;

TextBox1.Text = string.Empty;

}

protected void Button3_Click(object sender, EventArgs e)

{

if (string.IsNullOrEmpty(TextBox4.Text) || string.IsNullOrEmpty(TextBox1.Text))

{

Label5.Text = "Please Enter Some Values";

Label5.ForeColor = System.Drawing.Color.Red;

}

else

{

Arthmetic result = GetMulResult();

Label5.Text = String.Format("Multiplication Result is: {0}", result(double.Parse(TextBox4.Text), double.Parse(TextBox1.Text)));

Label5.ForeColor = System.Drawing.Color.Green; TextBox4.Text = string.Empty; TextBox1.Text = string.Empty;

}

protected void Button4_Click(object sender, EventArgs e)

{

if (string.IsNullOrEmpty(TextBox4.Text) || string.IsNullOrEmpty(TextBox1.Text))

{

Label5.Text = "Please Enter Some Values";

Label5.ForeColor = System.Drawing.Color.Red;

}

else

{

Arthmetic result = GetDivResult();

Label5.Text = string.Format("Division Result is: {0}", result(double.Parse(TextBox4.Text), double.Parse(TextBox1.Text)));

Label5.ForeColor = System.Drawing.Color.Green;

TextBox4.Text = string.Empty; TextBox1.Text = string.Empty;

}

private Arthmetic GetAddResult()

{

Arthmetic result = GetAdd; return result;

}

private Arthmetic GetSubResult()

{

Arthmetic result = GetSub; return result;

}

private Arthmetic GetMulResult()

{

Arthmetic result = GetMul; return result;

}

private Arthmetic GetDivResult()

{

Arthmetic result = GetDiv; return result;

}

public double GetAdd(double a, double b)

{

return a + b;

}

public double GetSub(double a, double b)

{

return a - b;

}

public double GetMul(double a, double b)

{

return a * b;

}

public double GetDiv(double a, double b)

{

return a / b;

}

}

Step 4: The output for the application is shown below: