I'm trying to deploy an MVC3 app on IIS7.5. But loading the page gives a "Server Error in '/' Application." message, with no more specific information about what went wrong.

Now my first idea was to try to get IIS to tell me the error message. To this end, I:

1) Added the <customErrors mode="Off" /> directive in Web.config. I still got no detailed error message.

2) Some searching indicated that sometimes, this "wasn't enough", and that you needed to add <httpErrors errorMode="Detailed" /> and <asp scriptErrorSentToBrowser="true" /> under <system.webServer></system.webServer>. Still no error message.

I'm now entertaining the thought that IIS actually has no error message to give me. I'm thinking this is a problem with my server configuration, and not with the app, so that I can't expect a stack trace etc like I'd expect with an application error.

So how do I figure out what's wrong?

Here's my setup:

My site is running in the "ASP.NET v4.0" Application Pool, using the integrated pipeline. It's running on the .NET 4.0 framework (I've registered .NET 4 with IIS using aspnet_regiis.exe to be sure).

I've enabled tracing of failed requests, and see in the error log that a MODULE_SET_RESPONSE_ERROR_STATUS warning has been triggered. ModuleName: AspNetInitializationExceptionModule. This doesn't make me any wiser, but maybe someone else can decode it.

Any thoughts on things I could try would be greatly appreciated.


Resolved this: In the file C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Config\web.config the server had this directive:

<trust legacyCasModel="true" /> 

I removed that, and now things run fine!

  • Can't see your directive
    – Greg B
    Aug 3 '12 at 12:34

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