Answers for "how to make postgresql unique in entity framework core entity model"

ef code first unique constraint

//single index
[Index("IX_First", IsUnique = true)]
public int FirstColumn { get; set; }

// composite index
[Index("IX_FirstAndSecond", 1, IsUnique = true)]
public int FirstColumn { get; set; }

[Index("IX_FirstAndSecond", 2, IsUnique = true)]
public int SecondColumn { get; set; }

how to set unique constraint from EF core

protected override void OnModelCreating(ModelBuilder builder)
{
    builder.Entity<User>()
        .HasIndex(u => u.Email)
        .IsUnique();
}