Ajax control intellisense did't work in Content Page??

Ajax control intellisense did't work in Content Page?? showing red underline in ScriptManager, UpdatePanel and ContentTemplate tags have the little red-squiggly lines underneath them...

http://weblogs.asp.net/scottgu/archive/2006/11/16/gotcha-lost-html-intellisense-within-asp-net-ajax-controls.aspx


The problem apparently comes from a failed attempt to wrap all AJAX controls with same asp: prefix as it is with the regular ASP.NET controls. So once you teach AJAX not to use asp: prefix, but for example the good ol' atlas:, confusion disappears and things start working fine again.

To fix that, you need to visit web.config, section system.web / pages / controls and replace all tagPrefix="asp" attributes with, for example, tagPrefix="atlas". After that, you need to use the same prefix throughout the application, thus no more asp:UpdatePanel, but atlas:UpdatePanel. After this operation intellisense starts working again, and no more screwed up markup or compilation errors.