Why do I always get an HTTP 500 - Internal Server Error when debugging a web app under IIS 7.5?

Question

I am trying to get Orchard CMS running under IIS, but I keep getting an HTTP 500 response. I have built and run the source code from within VS2012, but even with exceptions set to break when thrown, VS doesn't break, and I still get a very unhelpful and opaque HTTP 500 response. I created a new web site called Orchard, pointing to the source folder of the web app, i.e. C:\Development\Orchard.Source.1.6\src\Orchard.Web, and bound it to host name orchard.local, which I added to my hosts file under 127.0.0.1. I have read that I need to set file system permissions for IIS_IUSRS when running the web site under IIS; I don't know if I still do for debugging under VS. I would have though VS would take care of that. Then, for some reason I don't have that group, I only have an IIS_WPG group, which is supposed to be for IIS6. How can I diagnose what is causing this Internal Server Error if I can't even get VS to break on the exception?

Accepted Answer

This was happening because I installed IIS after Visual Studio, so ASP.NET 4 wasn't registered. I solved it by running

```
C:\Windows\Microsoft.NET\Framework\v4.0.30319\aspnet_regiis -i
```

Why do I always get an HTTP 500 - Internal Server Error when debugging a web app under IIS 7.5?

Solution

Problem