Question

I’m defining POCO’s, used with the Code First capabilities of Entity Framework 4.0.

Part of my data comes from an external source, and for that data I need to keep the identity column value identical to that of the external source, I sometimes need to set the ID myself. But for the same entities I sometimes don’t have an Id and would like an Auto increment like behavior.

Is it possible to define the POCO in such a way, that when I set the value it would use it, and when I don’t, it would auto increment?
According to this mySQL forum answer mySQL is supposed to handle this scenario pretty well, but it seems that with the Entity Framwork doesn’t…

Answer 1

Following on from Lari’s answer, I would suggest writing a stored procedure which sets identity_insert on, inserts records and then off afterwards.

I’d then import that as a function import and then using that inside perhaps an extension method on the entity type itself, or just as a function on the object context.

That way you can a standard:

var user = new User("John"); 
entities.Add(user);
entities.SaveChanges(); 

Type thing, when you want to use the auto incrementing number, and then use something like:

entities.CreateUser("John"); // This would be the SP

That way you could conditionally use one method or the other. It’s not automatic, but would enable you to use either.