Integrate ASP. NET Ajax with SharePoint

Official reference to integrating ASP. NET Ajax with SharePoint

If you do not configure it, Ajax control labels may not be identified,

If you have installed. netframework3.5 or above, your system. Web. extensions should be 3.5.0.0

You do not need to download and install ASP. NET 2.0 Ajax Extensions 1.0,

Similarly, you need to change all official versions 1.0.61025.0 to 3.5.0.0,

If you have installed ASP. NET 2.0 Ajax Extensions 1.0, you will be notified that the same space appears in different versions.ProgramSet,

You need to uninstall 1.0 and clear the related assembly in the app_bin and bin directories at the same time. Otherwise, the error will remain.