IIS7 Overrides customErrors when setting Response.StatusCode?

Question

Having a weird problem here. Everybody knows that if you use web.config's customErrors section to make a custom error page, that you should set your Response.StatusCode to whatever is appropriate. For example, if I make a custom 404 page and name it 404.aspx, I could put <% Response.StatusCode = 404 %> in the contents in order to make it have a true 404 status header.

Follow me so far? Good. Now try to do this on IIS7. I cannot get it to work, period. If Response.StatusCode is set in the custom error page, IIS7 seems to override the custom error page completely, and shows it's own status page (if you have one configured.)

Has anyone else seen this behavior and also maybe know how to work around it? It was working under IIS6, so I don't know why things changed.

Update: This is not the same as the issue in http://stackoverflow.com/questions/347281/asp-net-custom-404-returning-200-ok-instead-of-404-not-found

Answer 1

By default IIS 7 uses detailed custom error messages so I would assume that Response.StatusCode will equal 404.XX rather than just 404.

You can configure IIS7 to use the simpler error message codes or modify your code handling the more detailed error messages that IIS7 offers.

More info available here: http://blogs.iis.net/rakkimk/archive/2008/10/03/iis7-enabling-custom-error-pages.aspx

Further investigation revealed I had it the wrong way around - detailed messages aren't by default but perhaps they've been turned on, on your box if you're seeing the different error messages that you've mentioned.

Answer 2

I had the same question.

Already answered here http://stackoverflow.com/questions/347281/asp-net-custom-404-returning-200-ok-instead-of-404-not-found.

Answer 3

Solved: It turns out that "Detailed Errors" needs to be on in order for IIS7 to "passthrough" any error page you might have. See http://forums.iis.net/t/1146653.aspx

Answer 4

Set existingResponse to PassThrough in system.webServer/httpErrors section:

  <system.webServer>
    <httpErrors existingResponse="PassThrough" />
  </system.webServer>

More information: What to expect from IIS7 custom error module

Answer 5

The easiest way to make the behavior consistent is to use Response.TrySkipIisCustomErrors and set it to true. This will override the IIS global error page handling from within your page.

More info here: http://www.west-wind.com/weblog/posts/745738.aspx