When deploy a ASP.NET application to a new server, error message below shown:

Could not load file or assembly 'Microsoft.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies. The system cannot find the file specified.



This is the steps to solve this problem:

1. Copy AjaxControlToolkit.dll and AjaxControlToolkit.pdb version 1.0.61025.0 from my development machine to my ASP.NET App bin folder. (i install my AjaxControlToolkit in C:\Program Files\Microsoft ASP.NET\ASP.NET 2.0 AJAX Extensions\AjaxControlToolkit)

2. Copy System.Web.Extensions.dll (C:\WINDOWS\assembly\GAC_MSIL\System.Web.Extensions) and System.Web.Extensions.Design.dll (C:\WINDOWS\assembly\GAC_MSIL\System.Web.Extensions.Design) from my development machine to my ASP.NET App bin folder.

3. Run the application and it’s works.

Alternatively, we can solve the problem by installing AJAX.NET and AjaxControlToolkit to the server. Hope it helps