One of the things which was not clear to me when IIS7 configuration system was written was how configuration system merges all the configuration data available and then decide what values are effective for the current request. One of confusions came from the fact that I assumed that IIS modules try to read the values for the current URL and then keep moving up till it finds the attribute explicitly defined in a configuration file. This is part true for the configuration system but never for the modules. All modules do is ask the configuration system for a merged view of a particular configuration section for a configuration path which usually corresponds to the URL of the requested page.

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-Kanwal