Entity Framework 4.1 - Creating primary key values

0
votes

Quick info:

  • Using EF 4.1 Code First.
  • Using POCO classes with no attribute decoration.
  • Using fluent configuration in EntityTypeConfiguration<> classes to map POCO to database.
  • Following DDD pattern, using generic repositories, aggregate roots, specification, etc.

Problem:

For entities with the primary key set as identity, DatabaseGeneratedOption.Identity should work fine.

However, in our current schema there is an "interesting" way to create primary keys. A stored procedure is called that create the "next" unique key to use (same sproc is called for several different tables to ensure a unique key across all of them). This was from a legacy structure that I'm not going to get into in this post, but I need to be able to implement it.

I am setting the map to DatabaseGeneratedOption.None. What is the best approach to handling the retrieval of the new id right before inserting a record? Is there an event I can handle on the DbContext?

Thanks!

1
stored-proceduresprimary-keyentity-framework-4.1identity

1 Answers

1
votes

Values of DatabaseGeneratedOption set how EF deals with a property:

  • None - standard property. EF will load its value during select, allow application to modify the value and persist the value.
  • Identity - EF expects that this property will be set by the database when the record is inserted. EF will auto load this value back to entity when the record is inserted. It doesn't have to be identity column in the database - it can be value generated by trigger as well. Application cannot set value for property marked as identity
  • Computed - EF expects that this property can change in the database after each modification. It reloads the value after every insert or update. Application cannot set value for property marked as identity.

So if you want to call the procedure yourselves in your application you must use None. If you for example decide to use before insert trigger to execute the procedure you must use Identity.

DatabaseGeneratedOption.Identity means that value will be set in the database when the record is inserted. DatabaseGeneratedOption.Computed means that value will be set in the database each time the record is updated.