DropDownCheckBoxes: Introduction

DropDownCheckBoxes is a server control for ASP.NET web forms which provides the functionality of a standard CheckBoxList control in a form of a drop down list (the standard DropDownList control doesn't have any multi-select option). The key benefit of such approach is that it keeps space on a web page by dynamically displaying check boxes. The image bellow shows a sample use of the control:


About control

Browser compatibility: FireFox, Safari, Chrome, Opera (latest versions, May 2011), Internet Explorer 8.0

Server side: ASP.NET Web Forms 3.5, 4.0, can work with both synchronous postbacks and asynchronous when the control is placed within UpdatePanel control

The control is directly inherited from CheckBoxList control and thus can be used in place of it (easy migration is possible):

public class DropDownCheckBoxes : CheckBoxList, IPostBackEventHandler
{
...

The assembly containing control class also has embedded web resources used by the control which are automatically streamed to the browser:

• Client side JavaScript
• CSS file
• Button images
• jQuery script

Note: The jQuery JavaScript library is required for control proper functioning. The library is delivered within the assembly and is automatically referenced whenever the control is added to a page. To avoid duplicate references this behavior can be turned off by setting 'IncludeJqueryScript' property.

Getting started

The process of adding the control to project is absolutely the same as for other server controls.

1. In order to start using the control in you ASP.NET application get the control assembly from project's download page.

2. After you have DropDownCheckBoxes.dll downloaded you should add references to the assembly. Right click the web application project node in the solution explorer, choose 'Add reference' and in the dialog appeared find path to the downloaded .DLL file.


3. Register the control by adding web.config setting (if there's already <system.web><pages><controls> section - update it and don't create a duplicate):

<system.web>
   <pages>
       <controls>
           <add tagPrefix="asp" namespace="Saplin.Controls" assembly="DropDownCheckBoxes"/>
       </controls>
   </pages>
</system.web>

4. Put the control to .aspx page

<asp:DropDownCheckBoxes ID="yearsDropDownCheckBoxes" runat="server">
</asp:DropDownCheckBoxes>

The project page at Codeplex can be found here.