Alternate Keys (Unique Constraints)


The configuration in this section is applicable to relational databases in general. The extension methods shown here will become available when you install a relational database provider (due to the shared Microsoft.EntityFrameworkCore.Relational package).

A unique constraint is introduced for each alternate key in the model.


By convention, the index and constraint that are introduced for an alternate key will be named AK_<type name>_<property name>. For composite alternate keys <property name> becomes an underscore separated list of property names.

Data Annotations

Unique constraints can not be configured using Data Annotations.

Fluent API

You can use the Fluent API to configure the index and constraint name for an alternate key.

class MyContext : DbContext
    public DbSet<Car> Cars { get; set; }

    protected override void OnModelCreating(ModelBuilder modelBuilder)
            .HasAlternateKey(c => c.LicensePlate)

class Car
    public int CarId { get; set; }
    public string LicensePlate { get; set; }
    public string Make { get; set; }
    public string Model { get; set; }