See this example :
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default3.aspx.cs" Inherits="Default3" %>
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title></title>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:CheckBoxList ID="CheckBoxList1" runat="server" AutoPostBack="True" Height="31px" OnSelectedIndexChanged="CheckBoxList1_SelectedIndexChanged" Width="140px">
<asp:ListItem>Adrotator</asp:ListItem>
<asp:ListItem>BulletedList</asp:ListItem>
<asp:ListItem>Button</asp:ListItem>
<asp:ListItem>Calendar</asp:ListItem>
<asp:ListItem>DropDownList</asp:ListItem>
</asp:CheckBoxList>
<br />
</div>
<asp:Label ID="Label1" runat="server"></asp:Label>
</form>
</body>
</html>
Codebehind
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
public partial class Default3 : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
}
protected void CheckBoxList1_SelectedIndexChanged(object sender, EventArgs e)
{
foreach (ListItem item in CheckBoxList1 .Items)
{
if (item.Selected)
{
Label1.Text += item.Text;
}
}
}
}