In this article we will learn how to create a new Ajax extender from scratch, which expands the properties of ASP.NET controls, by adding a
custom Tooltip behavior that targets all types of web controls dragged to your
page.
The article also covers both using and creating a new Ajax extender from scratch.
I recommend that you download the source code, which
contains the code of the extender with a sample website; you can look at it in
more detail.