None of the ASP.NET Ajax library (not to be confused with ASP.NET AJAX) was officially released, and development on it stopped before its completion. You should not use it. I wrote an article on this subject.
In the same team, Microsoft introduced a new script loader, DeferJS, which is the next logical evolution of Sys.require. Here you can find the latest version: https://github.com/BorisMoore/JsDefer
source share