Scenario: I deployed an application as a virtual directory under the default site and my application threw a HTTP 500 error.
Resolution: The reason was that the default site and my virtual directory that was configured as an application had common keys (keys with the same name). I removed the key from the application in the virtual directory and the problem went away. One way to find any config issues in IIS7 is to open the configuration editor in IIS7 for the site you are troubleshooting. The configuration editor will throw specific exceptions if it cannot successfully open the config which is how I found the issue with duplicate keys.
Resolution: The reason was that the default site and my virtual directory that was configured as an application had common keys (keys with the same name). I removed the key from the application in the virtual directory and the problem went away. One way to find any config issues in IIS7 is to open the configuration editor in IIS7 for the site you are troubleshooting. The configuration editor will throw specific exceptions if it cannot successfully open the config which is how I found the issue with duplicate keys.
