>You've done well, I think
>
>Your original question : Is it possible without having a separate project for this class?

Well, nothing is simple in the .NET world :(

When I try to debug the page where I added this custom class I'm now getting

Error 124 Assembly 'AjaxControlToolkit, Version=3.0.20229.20843, Culture=neutral, PublicKeyToken=28f01b0e84b6d53e' uses 'System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' which has a higher version than referenced assembly 'System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35'

Which is a bit strange why does it say about AJAX instead of my new control?