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. stackoverflow.com/questions/23892553/… — Tejus
– Tejus, Commented Sep 18, 2018 at 7:12

Collin Barrett · Accepted Answer · 2018-09-20 19:07:55Z

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, 2018 at 19:07

answered Sep 19, 2018 at 17:58

Collin Barrett

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2 Comments

Isaac Kleinman Over a year ago

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.

Collin Barrett Over a year ago

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: github.com/collinbarrett/FilterLists/commit/…

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