Asp.net: failed to Load file or assembly "system. Web. Extensions, version = 1.0.61025.0, culture = neutral, publickeytoken = 31bf3

When a. NET Framework 3.5 project is migrated to 2.0, the preceding error is reported in Web. config because it needs to be integrated with other members. Add the selection item "ajaxcontroltoolkit. dll" again.

Find the following instructions on the Internet and try again.

Use Ajax in vs2005:

When you use Visual Studio 2005 to develop Ajax content, you must first install the Ajax Control Toolkit. You can download it here:
Http://www.codeplex.com/AtlasControlToolkit/Release/ProjectReleases.aspx? Releaseid = 1425

Download the first one and decompress it.
In the first folder, install "ajaxcontrolextender. VSI ".

After installation, find ajaxcontroltoolkit. dll under samplewebsite \ bin in the fourth folder, and load it by selecting items, the following error may be returned:
SlaveProgramAn error occurred while loading the set "... \ ajaxcontroltoolkit. dll ".
"Failed to 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 specified file ."
Or
... Cocould 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.

Click to downloadASP. NET 2.0 Ajax Extensions 1.0
Http://www.microsoft.com/downloads/details.aspx? Familyid = ca9d90fa-e8c9-42e3-aa19-08e2c027f5d6 & displaylang = en

After automatic installation, reload ajaxcontroltoolkit. dll again, and the installation will pass smoothly.