File Type and Extension Validation not working in AJAXControlToolKit AsyncFileUpload Control

Hi, I tried this tutorial http://www.aspsnippets.com/Articles/File-type-and-extension-validation-in-ASP.Net-AsyncFileUpload-Control-using-JavaScript.aspx It doesn't work with  and vs 2010, and ajax control toolkit 4 ( I downloaded from link below and vs 2010) and It doesn't work with ajaxcontroltollkit 3.5 I downloaded from same link. but when i put Your AjaxControlToolkit.dll in bin folder of my project it works fine.

I downloded the same version of tolkit.dll as yours (3.0.30930.0) and I worked for me.

but I'd like to use version 4.

what's the problem? Please help me! Thanks. bahare