I've seen a few different posts about this, but they are mostly outdated and didn't resolve my issue. I put together some simple steps we took to make it work.
We had a project that originally used the AjaxControlToolkit on some pages. All new development used Telerik controls. There were issues performing Ajax operations despite the AjaxControlToolkit not even being registered on a page. This was the only fix I could find.
- Remove the existing
AjaxControlToolkit reference from the project and delete the
AjaxControlToolkit.DLL from the bin directory on the remote server (if it
- Remove any
AjaxControlToolkit assembly registrations at the top of the page markup
(if they exist)
- Install the
AjaxControlToolkit via the NuGet package manager in Visual Studio (update
the tag prefix as needed)
- In the MasterPage markup, disable combining scripts in
<telerik:RadScriptManager runat="server" ID="RadScriptManager1" EnableScriptCombine="false"></telerik:RadScriptManager>
I hope this helps someone else down the road. A better solution is to replace the AjaxControlToolkit controls with Telerik controls, but this gets us by until we make time to do that.