ASP.NET 4.0, Extensionless Urls, and the eurl.axd errors

Apparently ASP.NET 4.0 has something special for “extensionless URLs”—which is what we get from using ISAPI_Rewrite on our Windows Server 2003 machines. The symptom we were seeing was that the URL Rewriting kept unexpectedly returning something similar to this:

eurl.axd/ADkfjsFiSofmaWOeiejrlErF

so rewriting something like:

/myrewrite/articleID/articleName/

would end up rewriting to:

/myrewrite.aspx?id=eurl.axd/ADkfjsFi…..

On the server’s Registry Editor (regedit) I followed this article’s “option 3” and turned off the EnableExtensionlessUrls, which is a DWORD set to 0 (zero) within HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\ASP.NET\4.0.30319.0 —then you must run theh iisreset command-line tool.