How to use CheckBox Control in ASP.NET

Introduction
The Checkbox control creates a check box that can be selected by clicking it. The control exists within the System.Web.UI.WebControls namespace. The Checkbox control displays checkmarks that allow the user to toggle between a True or False condition.

Public Properties of the Checkbox Class
AutoPostBack : Obtains a value showing , if the CheckBox state automatically post back to the server when clicked or not.
Checked : Obtains a value showing , if the CheckBox control is checked or not.
Text : Obtains the text label associated with the CheckBox control.

Example of CheckBox control in ASP.NET

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %>

<!DOCTYPE html>

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title></title>
</head>
<body>
<form id="form1" runat="server">
<div>
<h2>CHECKBOX EXAMPLE</h2>
<br/>
<asp:CheckBox ID="CheckBox1" runat="server" AutoPostBack="True" OnCheckedChanged="CheckBox1_CheckedChanged" Text="Apple" />

<br />
<asp:CheckBox ID="CheckBox2" runat="server" AutoPostBack="True" OnCheckedChanged="CheckBox2_CheckedChanged" Text="Mango" />

</div>
<asp:CheckBox ID="CheckBox3" runat="server" AutoPostBack="True" OnCheckedChanged="CheckBox3_CheckedChanged" Text="Orange" />
<br />
<br />
<asp:ListBox ID="ListBox1" runat="server" Height="145px" Width="112px"></asp:ListBox>
</form>
</body>
</html>

Codebehind Code

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

public partial class _Default : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{

}
protected void CheckBox1_CheckedChanged(object sender, EventArgs e)
{
if (CheckBox1 .Checked==true)
{
ListBox1.Items.Add(CheckBox1.Text);

}
else
{
ListBox1.Items.Remove(ListBox1.Items.FindByText(CheckBox1.Text));
}

}
protected void CheckBox2_CheckedChanged(object sender, EventArgs e)
{
if (CheckBox2.Checked == true)
{
ListBox1.Items.Add(CheckBox2.Text);

}
else
{
ListBox1.Items.Remove(ListBox1.Items.FindByText(CheckBox2.Text));
}

}
protected void CheckBox3_CheckedChanged(object sender, EventArgs e)
{
if (CheckBox3.Checked == true)
{
ListBox1.Items.Add(CheckBox3.Text);

}
else
{
ListBox1.Items.Remove(ListBox1.Items.FindByText(CheckBox3.Text));
}

}
}

Code Generate the following Output

This example shows when you select any one checkbox which is taken in this example then your checkbox Text add to the ListBox . If you unselect it then remove Text from the list.Because AutoPostBack property is working here.
ListBox1.Items.Remove() : If you want to remove item from list then use remove method of the list.
ListBox1.Items.FindByText() : If you want to search any item from the list then use FindbyText() method.