Generating Entity Keys

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+1 Q:

Generating Entity Keys

I have run into my first dissapointment with Entity Framework 4. It turns out that SQL CE, when used with EF4, does not support autogenerated primary keys. I get a System.Data.UpdateException from OnjectContext.SaveChanges() with this message:

Server-generated keys and server-generated values are not supported by SQL Server Compact.

So, now I have to manually generate keys for my entities. Assuming I want to use auto-incremented integer keys, what is the best way to go about generating and keeping track of the keys when using Entity Framework? Thanks for your help.

+1 A:

At the bottom of the link in your question is a suggested solution. See SQL Compact, Identity Columns and Entity Framework perhaps you might want to implement an extension method like the one outlined.

DaveB 2010-03-19 23:07:02

That's great--thanks!

David Veeneman 2010-03-20 01:30:45

Good answer, but unfortunately, the code on the linked page only works for unfiltered entity sets, since the extension method returns the max id in the entity set. So, I ended up using a GUID as the entity key. I created a partial class for each entity with this constructor code: this.ID = Guid.NewGuid()

David Veeneman 2010-03-20 22:30:13

i don't think David's ideal is a good ideal, however, i have no choise. Maybe CE will support autogenerated primary keys in next version.

gary 2010-06-09 03:13:15

Actually, SQL Compact does support autogenerated keys--apparently, it's EF4 that doesn't support autogenerated keys from SQL Compact. The blog post linked in my original question explains the problem.

David Veeneman 2010-07-23 15:05:35

ansaurus

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Generating Entity Keys

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