Is IIS performing an illegal character substitution? If so, how to stop it?

Question

Context: ASP.NET MVC running in IIS, with a a UTF-8 %-encoded URL.

Using the standard project template, and a test-action in HomeController like:

<

Answer 1

Once Upon A Time, URLs themselves were not in UTF-8. They were in the ANSI code page. This facilitates the fact that they often are used to select, well, pathnames in the server's file system. In ancient times, IE had an option to tell whether you wanted to send UTF-8 URLs or not.

Perhaps buried in the bowels of the IIS config there is a place to specify the URL encoding, and perhaps not.