Thursday, March 10, 2011

The worst thing about Entity Framework

Generally, I like Entity Framework, especially the newest version (part of Visual Studio 2010). The absolute worst thing about it is the error message you can get when you are hooking-up your POCO files to an entity model. The error message is: "Mapping and metadata information could not be found for EntityType [...]"

EF tells you in which class the error is located, but that's it. It could be any of the properties that don't work! If you have a database table with 20 or 50 fields, good luck in tracking down the error. The best info I've found is that the error can be caused by:
  • Misspelled properties (case-sensitive!)
  • Properties missing in the POCO class
  • Type mismatches between the POCO and entity-type (e.g., int instead of long)
  • Enums in the POCO (EF doesn't support enums right now as I understand)
It has got to be the worst error message I've seen from Microsoft in a long time.

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