Entity Framework: Add Unique Constraint to existing property

Question

I have an existing model, SomeModel, which contains a property Prop. I'd like to enforce that the values of Prop be unique.

To this end, I'm adding the following to my model:

public static void OnModelCreating(ModelBuilder modelBuilder)
{
    modelBuilder.Entity<SomeModel>()
      .HasAlternateKey(a => a.Prop);
}

but ef migrations isn't picking up the change.

How can I correct this?

This may be helpful. https://stackoverflow.com/questions/23892553/creating-unique-index-with-entity-framework-6-1-fluent-api — Tejus, Sep 18 '18 at 07:12

Collin Barrett · Answer 1 · 2018-09-20T19:07:55.377

1

This works for me with EF Core on an already existing model. add-migration picks up the change.

public static void OnModelCreating(ModelBuilder modelBuilder)
{
    modelBuilder.Entity<SomeModel>()
                .HasIndex(u => u.Prop)
                .IsUnique();
}

edited Sep 20 '18 at 19:07

answered Sep 19 '18 at 17:58

Collin Barrett

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I've found that this override only works if it's there when you first create the model - not if you add it at some later point. – Isaac Kleinman Sep 20 '18 at 16:49
Hmm, you are using EF Core, correct (inferred from the tag)? I just tested it on an existing model in one of my projects, and this picked it up just fine. Maybe it depends on your EF provider? My example: https://github.com/collinbarrett/FilterLists/commit/d4c2198791e657cc20bdb3d0a51490a0d02ad9c5 – Collin Barrett Sep 20 '18 at 18:17

Entity Framework: Add Unique Constraint to existing property

1 Answers1