Unique Constraint in Entity Framework Code First

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As far as I can tell, there’s no way to do this with Entity Framework at the moment. However, this isn’t just a problem with unique constraints… you may want to create indexes, check constraints, and possibly triggers and other constructs too. Here’s a simple pattern you can use with your code-first setup, though admittedly it’s not database agnostic:

public class MyRepository : DbContext {
    public DbSet<Whatever> Whatevers { get; set; }

    public class Initializer : IDatabaseInitializer<MyRepository> {
        public void InitializeDatabase(MyRepository context) {
            if (!context.Database.Exists() || !context.Database.ModelMatchesDatabase()) {
                context.Database.DeleteIfExists();
                context.Database.Create();

                context.ObjectContext.ExecuteStoreCommand("CREATE UNIQUE CONSTRAINT...");
                context.ObjectContext.ExecuteStoreCommand("CREATE INDEX...");
                context.ObjectContext.ExecuteStoreCommand("ETC...");
            }
        }
    }
}

Another option is if your domain model is the only method of inserting/updating data in your database, you could implement the uniqueness requirement yourself and leave the database out of it. This is a more portable solution and forces you to be clear about your business rules in your code, but leaves your database open to invalid data getting back-doored.

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