1. Install the ASP.NET Ajax 1.0 extensions here http://www.microsoft.com/downloads/details.aspx?FamilyID=ca9d90fa-e8c9-42e3-aa19-08e2c027f5d6&displaylang=en
2. Download this (AjaxControlToolkit.zip)
   and unpack it to a folder on your local computer.
3. Open Visual Studio, right click on Tools and create a new tab. Call it Ajax Controls.
   Right click the tab and pick Choose Items…
4. Browse to the directory where you unpacked the toolkit, browse to the Sample Web Site
   folder, then the bin directory. Choose the AjaxControlToolkit.dll and your list should
   be populated with the new controls.

If you want to see a sample of the controls in action, go here (http://www.asp.net/AJAX/AjaxControlToolkit/Samples/Default.aspx)

So for a recent research project, I decided I would look into the LinqDataSource’s
control GroupBy and OrderGroupBy attributes
to see if they could be used to help me build a grid that supports grouping.ÂÂ
Below is the final screen shot for my reference application.  The grid shows
the rows in the Northwind Orders table – grouped by the customer that placed the order.ÂÂ
The group of orders for each customer can be expanded/collapsed by clicking on the
plus/minus icon (no postback required).  Read on if you are interested in the
details.  If you download the code, make sure to update the connection string
in the web.config to point to your Northwind database.

Matt
Berseth: Building a Grouping Grid with the ASP.NET 3.5 LinqDataSource and ListView
Controls