Entity Framework Core add unique constraint code-first

Question

I can\'t find way to add a unique constraint to my field with using attribute:

public class User
{
    [Required]
    public int Id { get; set; }

    [Requi         


        

Answer 1

None of these methods worked for me in .NET Core 2.2 but I was able to adapt some code I had for defining a different primary key to work for this purpose.

In the instance below I want to ensure the OutletRef field is unique:

public class ApplicationDbContext : IdentityDbContext
    {
        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            base.OnModelCreating(modelBuilder);
            modelBuilder.Entity()
                .HasIndex(o => new { o.OutletRef });
        }
    }

This adds the required unique index in the database. What it doesn't do though is provide the ability to specify a custom error message.