If I try to add an extender in design mode I select the control from the dialog, but when I press OK I get and error -
Unable to reference extender assemply AjaxControlToolkit.....
If I add the extender manually in source it works - I have the correct version of Ajax - the extenders all are in the Toobox, the dlls are in the bin folder and made the modifications as decribed by Stephen Walther http://stephenwalther.com/archive/2012/09/20/september-2012-release-of-the-ajax-control-toolkit.aspx