IIS express: Cannot add duplicate collection entry of type 'add' with unique key attribute 'name' set to

Question

In Visual studio, Solution->Web.Project->Properties->Web, I have changed my Project Url from http://localhost:51123/ to http://localhost:51123/NewProj

Answer 1

The answer that @orjanto posted solved the problem for me, but I had an additional problem on top of that. After fixing, Internet Explorer still thought that my HTML page was a directory instead of a file.

I had duplicates in my IIS Express config file:

Note the path="/login.html" in the second entry.

My page was redirecting to "localhost:57018/login.html/" like it was a directory.

Removing the second entry fixed the problem with the configuration file duplicates, however I continued to have a problem where Internet Explorer seemed to think that /login.html/ was a directory (Internet Explorer 11). To diagnose the problem, I checked Chrome and Chrome worked fine.

I went into Internet Explorer, went to Tools > Internet Options > General Tab. Then under "Browsing History" section, I deleted History, Cookies and Website Data, & Temp. Internet Files.