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A Multiple Selection DropDownList (a CheckBoxList Inside a DropDownList)

By , 19 Mar 2010
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This ascx user control, the MultiCheckCombo, allows the user to select more than one option inside a DropDownList. The different items that are being checked are being copied in the box area of the control.

The great thing of this control is that it doesn't close the check panel until you click outside the control. Example: you can check more than one item at once.

In ASP.NET C#, if you need a web control that allows the user to check more than one option in a DropDownList, you can use this user control freely.


Well, first of all, this control was made in Microsoft Visual Studio 2008, with .NET 3.5 (2.0) and was written in C#. To use it, you need to have properly installed the AjaxControlToolkit in your project.

Using the Code

Again: You need to have installed the AjaxControlToolkit in your project.

This control is fairly easy to implement. Simply copy the 3 ascx files into your project.

Then replace the namespace in both ascx and ascx.cs files with [YourProjectName].MultiCheckCombo.

E.g.: Let's suppose your project's name is TestMultiCheck, replace in the ascx file the Control tag with the name of your namespace/project:

<%@ Control Language="C#" AutoEventWireup="true" CodeBehind="MultiCheckCombo.ascx.cs" 
    Inherits="TestMultiCheck.MultiCheckCombo" %>

And in your ascx.cs file, change the namespace to:

namespace TestMultiCheck

Well, then drag and drop the main file (MultiCheckCombo.ascx) to your Page Designer.

You may drag the control inside or outside an UpdatePanel, but you need a ScriptManager at the beginning of the body tag of your aspx page.

<asp:ScriptManager ID="ScriptManager1" runat="server"> </asp:ScriptManager> 

When you drag the control, the following line should be added automatically to the beginning of your aspx page:

<%@ Register src="MultiCheckCombo.ascx" tagname="MultiCheckCombo" tagprefix="uc1" %>

And the code of the control looks like this (it also will be added automatically):

<uc1:MultiCheckCombo ID="MultiCheckCombo1" runat="server" />        

Then, in the code behind (C#), you have to fill the values of the control.

You can fill it with an ArrayList or with an OdbcDataReader.

A: Easy mode: Filling the MultiCheckCombo with an ArrayList:

ArrayList array = new ArrayList();
for (int i=0;i<100;i++) array.Add(i.ToString());

B: Other option is to fill the MultiCheckCombo with an OdbcDataReader:

OdbcConnection con = /* get YOUR connection string*/
OdbcCommand cmd = new OdbcCommand();
cmd.Connection = con;
cmd.CommandText = "select text,id from ...........";
OdbcDataReader dr = cmd.ExecuteReader();
MultiCheckCombo1.AddItems(dr, "text", "id");

And that's it. You can now test it.

Some important properties of this controls are:

MultiCheckCombo1.WidthCheckListBox = 200; //Set the Width of the CheckBoxList inside DDL.
MultiCheckCombo1.Width = 250; //Set the Width of the DropDownList
MultiCheckCombo1.Enabled = true;
MultiCheckCombo1.fontSizeCheckBoxList = FontUnit.Small; 
MultiCheckCombo1.fontSizeTextBox = FontUnit.XSmall;
MultiCheckCombo1.Text; //Get or Set the Text shown in the Combo

Some important methods of this control are:

MultiCheckCombo1.unselectAllItems(); //Uncheck all of the Items of the CheckBox
MultiCheckCombo1.ClearAll(); //Delete all the Items of the CheckBox;

Points of Interest

I hope you can make it work. Cheers! ENJOY IT!

By the way, my e-mail is


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

About the Author

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Argentina Argentina
Systems Eng.

Comments and Discussions

GeneralWorks 100% PinmemberMember 104302042-Dec-13 3:40 
GeneralMy vote of 2 PinmemberSharma Richa15-Oct-13 19:49 
GeneralMy vote of 2 PinmemberOmniasis10-Oct-13 23:38 
Buggetting error Could not load type MultiCheckCombo PinmemberMember 100585969-Jul-13 0:41 
QuestionRead the selected checkbox values PinmemberRockstar_2-Jun-13 19:33 
GeneralMy vote of 5 PinmemberRockstar_2-Jun-13 19:23 
GeneralMy vote of 5 Pinmembercooldiv4u31-May-13 5:10 
GeneralMy vote of 5 Pinmemberganeshnarsale2-May-13 0:28 
BugDoes not work with several controls inside the same page. [modified] PinmemberJaviere ere24-Jan-13 4:24 
QuestionProblem while showing the values after selecting the checkbox in MultiCheckCombo Pinmembervaibhavpahade2005078-Jan-13 6:31 

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