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Editorial Team
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Asked: 2026-05-31T15:27:53+00:00

I am building an ASP.Net MVC 3 web application using Entity Framework 4.1 with

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I am building an ASP.Net MVC 3 web application using Entity Framework 4.1 with the Database First Approach.

I have just setup my solution with separate projects for the following:

  1. UI – MVC app
  2. Model – Class Library
  3. POCOs – Class Library
  4. Repositories – Class Library
  5. Services – Class Library

I have set this up a few times before without any trouble, but now when I try to create a controller in my MVC app, I get the following error:

Unable to retrieve metadata for 'Entityname'. An item with the same key has already been added.

This happens when I try to add any controller with an Entity for its Model class. I am stumped with this. I tried re-creating the model from the db and regenerated my POCO classes, but still this problem exists.

Can anyone please help?

Thanks.

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1 Answer

  1. Editorial Team

    I solved it. When Entity Framework created my entity data model, some of the names it gave to the navigation properties were a bit meaningless. I therefore edited a couple of these properties, however, I ended up naming two different navigation properties, with the same type of association, the same name. Needless to say EF didn’t like this. I renamed the offending navigation property. It was a tough one to fix as there were no compile errors from the model.

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