# .NET and More > ASP.NET And ASP.NET Core >  AjaxExtendersToolbox.dll

## DonaldJamesParker

I have decided to upgrade my Visual Studio 2012 Express to VS 2022 .  Now my development website doesn't work.  I'm getting an error that I believe deals with the AjaxToolbox (from what I found in my research anyway).  Error is this:  The following information can be helpful to determine why the assembly 'System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' could not be loaded.     

I have two files in my bin folder named AjaxExtentionsToolbox.Exclude and AjaxExtentionsToolbox.Refresh.Exclude  - I'm not sure what the exclude extension means but it seems that it directs the compiler to ignore it?   I tried to install a new AjaxExtensionsToolbox and got an error that the install process couldn't find a 2010, 2012, 2015, or 2019 version of Visual Studio.  

Can anybody confirm this is a problem with AJAX and perhaps give me pointers on how to resolve it.

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