asp.net - CustomErrors does not work when setting redirectMode="ResponseRewrite"

Question

In a old site, I was changing the way that CustomErrors works by adding redirectMode="ResponseRewrite" (new in 3.5 SP1):

<customErrors mode="RemoteOnly" defaultRedirect="Error.aspx" redirectMode="ResponseRewrite">
    <error statusCode="404" redirect="404.aspx" />
</customErrors> 

The thing is: it shows me the generic error page (the one that you get when you don't set customErrors. If I remove theredirectMode="ResponseRewrite" part, it works fine.

I'm sure 3.5 SP1 is installed in the server, because I use the same setting on other sites hosted in the same server.

Any ideas?

Answer 1

It is important to note for anyone trying to do this in an MVC application that ResponseRewrite uses Server.Transfer behind the scenes. Therefore, the defaultRedirect must correspond to a legitimate file on the file system. Apparently, Server.Transfer is not compatible with MVC routes, therefore, if your error page is served by a controller action, Server.Transfer is going to look for /Error/Whatever, not find it on the file system, and return a generic 404 error page!