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Wednesday, November 30, 2016

How long since you have seen the "Dictionary already contains ClassInfo ..." error for the Model Editor?

Old XAFers can remember this old sporadic issue caused by a Visual Studio bug that could not be fixed on the IDE side for years (learn more...). We were frustrated by it no less than our users, and this April (15.1.11+, 15.2.8+, 16.1+) we finally found a way to bypass this nasty behavior of an internal IDE assemblies cache on our side by changing the process of  loading assemblies at design time. This was quite a risky change, but so far our testing of many projects under various circumstances went well. We also have not received user reports on the original problem or other side effects with our designers since then (more than 8 months).

That said, I wanted to explicitly clarify with the XAF community whether it is really gone after our changes or not. Please leave a comment below on whether you have seen this error with the latest XAF versions OR you already cannot recall when it occurred last time. If this still bothers you, I would kindly ask you submit a ticket using the Support Center and attach a project where this behavior is stably reproducible, exactly as this kind guy did in the past.

My team and I look forward to hearing from you!


  1. Good to know Dennis - we where using xpand modeleditor plugin since years now to bypass this one. Seems it is time to use VS integrated one again :)


  2. I didn't see it for half a year or so - that would make sense!

    Krzysztof Krzysztof

  3. Agreed - haven't seen it in quite some time.

  4. We also use the eXpand editor as the integrated one was unusable due to this error.

  5. Works perfect now Dennis - thank you Guys!!

  6. Here the same - very good!

  7. Works fine here.
    I have seen the message a fews days ago, but this was because of a duplicate id in the model.

  8. Sometimes I still get the error in 16.1.4.
    Most of the time, I compile my base solution first. After that I copy the base assemblies to my main application using these as references. It ocurres when opening the application model in my main application

    f.e. Dictionary already contains ClassInfo 'MainModel.Common.BOModel.BoBase'. Possible reason: the assembly [MainModel.Common, Version=, Culture=neutral, PublicKeyToken=null] has been loaded twice.

    1. @Arjan: Would you please submit a ticket using the Support Center and attach a project where this behavior is reproducible (do not forget to specify the exact VS version)?