ASP.NET suddenly wants a trailing slash

Question

In an ASP.NET application, we have plenty (think, several dozen) of controller classes like this:

[RoutePrefix(\"some/thing/1.0\")]
public class SomeController :         


        

Answer 1

We have found the concrete cause of why the error started appearing now:

A call to MapSignalR had been commented out, and without it, a much older, presumably erroneous setting buried somewhere in the application's configuration files became active: A TransferRequestHandler whose path was specified as *. instead of just *.

Presumably, SignalR somehow overwrites that setting once initialized, so the issue never popped up for the past couple of years.

So, explicitly: The Web.config file contained the following line:

This had to be changed to

for the issue described here to go away.

(Unfortunately, this solution causes another problem.)