Recently upgraded the entire project to .NET 4.0 but when I debug javascript (using FireBug or Developer tools for IE9) it says the javascript file MicrosoftAjax.debug.js is still version 3.5 - is this an issue?
// Name: MicrosoftAjax.debug.js
// Assembly: AjaxControlToolkit
// Version: 3.5.40412.0
// FileVersion: 3.5.40412.2
// (c) 2010 CodePlex Foundation
You have to download new version of AjaxControlToolkit. Upgrading project does not apply to additional assemblies, libraries etc.
http://ajaxcontroltoolkit.codeplex.com/
Please give feedback in comment if i helped.