Figure 1

Figure 2

Recently, I was looking for a multiple selection
dropdownlist control for my new project. After spending some time researching
for it, I decided to put together all my finding in one web user control. This
web user control consists of an ASP.NET AJAX HoverMenuExtender, JavaScript,
StyleSheet and CheckBoxListExCtrl.
The final product will work with or without a masterpage and you can drag and
drop more than one instances of the control on to the page. This is not a
perfect control, feel free to modify it to tailor your requirement and share
your thoughts. Below is a step by step tutorial on how I have accomplished
this. Hope this tutorial will give someone an idea on how to use ASP.NET AJAX
HoverMenuExtender and create multiple selection dropdownlist.
Before we begin, this is the structure of my project.
Figure 3
