‘ProjectName.Program+Category’ was not mapped. Check that the type has not been explicitly excluded by using the Ignore method or NotMappedAttribute data annotation

If you follow the code from this blog http://blogs.msdn.com/b/adonet/archive/2011/03/15/ef-4-1-code-first-walkthrough.aspxthen you might hit the error “’ProjectName.Program+Category’ was not mapped. Check that the type has not been explicitly excluded by using the Ignore method or NotMappedAttribute data annotation.”

I repeat the code in below.



  publicstring CategoryId { get; set; }

  publicstring Name { get; set; }


  publicvirtualICollection<Product> Products { get; set; }





  publicint ProductId { get; set; }

  publicstring Name { get; set; }

  publicstring CategoryId { get; set; }


  publicvirtual Category Category { get; set; }



publicclassProductContext : DbContext


  public ProductContext()




  public DbSet<Category> Categories { get; set; }

  public DbSet<Product> Products { get; set; }



When comes to

static void Main(string[] args)


    using (var db = new ProductContext())


        // Add a food category

        var food = new Category { CategoryId = “FOOD”, Name = “Foods” };


        int recordsAffected = db.SaveChanges();



            “Saved {0} entities to the database, press any key to exit.”,






The error will throw at the line using (var db = new ProductContext()).

Maybe when the blogger blogs the EF 4.1 the console project is able to run Code First code. In VS 2012 the console project will not run this code. The code can be run in Web project.

You can also download a single solution from http://skydrive.live.com. The sample file name is WebAppCodeFirst.rar My MSN ID is chanmmn@hotmail.com.


About chanmingman

Since March 2011 Microsoft Live Spaces migrated to Wordpress (http://www.pcworld.com/article/206455/Microsoft_Live_Spaces_Moves_to_WordPress_An_FAQ.html) till now, I have is over 1 million viewers. This blog is about more than 50% telling you how to resolve error messages, especial for Microsoft products. The blog also has a lot of guidance teaching you how to get stated certain Microsoft technologies. The blog also uses as a help to keep my memory. The blog is never meant to give people consulting services or silver bullet solutions. It is a contribution to the community. Thanks for your support over the years. Ming Man is Microsoft MVP since year 2006. He is a software development manager for a multinational company. With 25 years of experience in the IT field, he has developed system using Clipper, COBOL, VB5, VB6, VB.NET, Java and C #. He has been using Visual Studio (.NET) since the Beta back in year 2000. He and the team have developed many projects using .NET platform such as SCM, and HR based applications. He is familiar with the N-Tier design of business application and is also an expert with database experience in MS SQL, Oracle and AS 400.
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