Sorry for being dumb here.
I'm getting the following error after updating the AjaxControlToolkit.dll on a site, after copying the new DLL to the bin folder;
Could not load file or assembly 'AjaxControlToolkit' or one of its dependencies. This assembly is built by a runtime newer than the currently loaded runtime and cannot be loaded.
After googling around to fix the issue, I changed the application pool on IIS (Version 7.5.7600) fromt he default site named pool to be ASP.NET Classic (I have also tried Integrated).
However I then get a 500 error when I try to navigate the site?
Can anyone direct me in the right direction please?