App_Code: Best In (Very) Small Doses

When I first started developing solutions on version 2.0 of the .NET Framework, I saw examples that had some logic in the App_Code folder. For things like base pages, I thought App_Code was perfect–and that’s how I use it today. When I started to see applications put their entire middle tiers in App_Code however, I thought that was a bad idea. Beyond not being able to unit test your components (and the consequences associated with a lack of unit testing, coverage, etc), it just seemed … wrong.

Fortunately, there are additional reasons to minimize the use of App_Code: