Where to get and how to install (or migrate) missing assemblies for ASP.NET server?

Question

I am migrating web apps to new hosting servers, but when I try to access them to test on the new server, I get all these assemblies not found errors like:

Configuration Error
Description: An error occurred during the processing of a configuration file required to service this request. Please review the specific error details below and modify your configuration file appropriately.

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

Source Error:

Line 28:        <compilation debug="false">
Line 29:            <assemblies>
Line 30:                <add assembly="System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"/>
Line 31:                <add assembly="System.Design, Version=2.0.0.0, Culture=neutral, PublicKeyToken=B03F5F7F11D50A3A"/>
Line 32:                <add assembly="System.Web.Extensions.Design, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/>

Does anyone know where you find these to install or how to migrate them over?

Answer 1

That's part of the ASP.Net AJAX kit.