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Posted 13 Sep 2011
Licenced CPOL

Easiest way to Create a Multiselect Dropdown in ASP.NET 4.0 using C#

, 22 Mar 2013
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A multiselect dropdown in ASP.NET.



In this article, I will show you how to create a multi-select control in ASP.NET. I will keep this article short and sweet so you can just use the code in your applications. Previously I referred to many codes for a multiselect dropdown but I found they were all a little complex to implement. So I decided to try it on my own. Let's see how I implemented this.


First, you must install AJAX controls in Visual Studio. I am using VS2010. This is because I am using the popup control extender to implement this control.

Using the code

Place a textbox in Design view and assign the popup extender for that textbox. An important thing to note here is you must place your textbox control within the UpdatePanel.

Afterwards, you create a panel and within this panel, you put a checkboxlist. You then assign this panel to the PopupControlID property of the popup extender.

Now take a look at this code:

<%@ Page Language="C#" AutoEventWireup="true" 

   CodeFile="multidropdown.aspx.cs" Inherits="_Default" %>

<%@ Register Assembly="AjaxControlToolkit" 

  Namespace="AjaxControlToolkit" TagPrefix="asp" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" 

<html xmlns="">
<head runat="server">
    <form id="form1" runat="server">
        <asp:ToolkitScriptManager runat="server">

        <asp:UpdatePanel ID="updatepanel1" runat="server">


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


                    ID="TextBox1_PopupControlExtender" runat="server"

                    Enabled="True" ExtenderControlID="" 


                    PopupControlID="Panel1" OffsetY="22">

                <asp:Panel ID="Panel1" runat="server" 

                     Height="116px" Width="145px" 

                     BorderStyle="Solid" BorderWidth="2px" 


                     ScrollBars="Auto" BackColor="#CCCCCC" 

                     Style="display: none">
                    <asp:CheckBoxList ID="CheckBoxList1" runat="server" 

                          DataSourceID="SqlDataSource1" DataTextField="holiday_name"

                         DataValueField="holiday_name" AutoPostBack="True"


                    <asp:SqlDataSource ID="SqlDataSource1" 

                          runat="server" ConnectionString="<%$ 
                          ConnectionStrings:employeedbConnectionString %>"

                        SelectCommand="SELECT [holiday_name] FROM [tblholidaymas]"> 

Here, you select the datasource from your SQL Server database.


Finally, we need to do one more modification in the code-behind. Each time we click the checkboxlist, the selected value will be added to the textbox control. So in the selected index changed event, you will place this 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 CheckBoxList1_SelectedIndexChanged(object sender, EventArgs e)
        string name = "";
        for (int i = 0; i < CheckBoxList1.Items.Count; i++)
            if (CheckBoxList1.Items[i].Selected)
                name += CheckBoxList1.Items[i].Text + ",";
        TextBox1.Text = name;

That's all.


This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


About the Author

Software Developer (Junior) CS1401
India India

Any fool can write code that a computer can understand. Good programmers write code that humans can understand.

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Comments and Discussions

GeneralMy vote of 5 Pin
C133722-Sep-11 23:45
memberC133722-Sep-11 23:45 
GeneralRe: My vote of 5 Pin
CS140123-Sep-11 0:37
memberCS140123-Sep-11 0:37 
QuestionBeware SQL Injection Pin
Stephen Inglish14-Sep-11 1:51
memberStephen Inglish14-Sep-11 1:51 
AnswerRe: Beware SQL Injection Pin
CS140114-Sep-11 2:40
memberCS140114-Sep-11 2:40 
GeneralRe: Beware SQL Injection Pin
Marcus Kramer14-Sep-11 3:11
memberMarcus Kramer14-Sep-11 3:11 
GeneralRe: Beware SQL Injection Pin
CS140114-Sep-11 3:21
memberCS140114-Sep-11 3:21 
GeneralMy vote of 5 Pin
karthi.mkr13-Sep-11 20:02
memberkarthi.mkr13-Sep-11 20:02 
GeneralRe: My vote of 5 Pin
CS140113-Sep-11 20:25
memberCS140113-Sep-11 20:25 
GeneralMy vote of 5 Pin
Professional manpreet13-Sep-11 8:41
memberProfessional manpreet13-Sep-11 8:41 
GeneralRe: My vote of 5 Pin
CS140113-Sep-11 18:40
memberCS140113-Sep-11 18:40 

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