The Fluent API HasData Method

The Entity Framework Core Fluent API HasData method is designed to help provide seed data for migrations to the specified entity. It can also be used to seed a database with data outside of a migration. This can be useful for testing purposes, when a database should start in a known state.

The following example illustrates seeding by adding an entry to the Authors table:

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    modelBuilder.Entity<Author>().HasData(
        new Author
        {
            AuthorId = 1,
            FirstName = "William",
            LastName = "Shakespeare"
        }
    );
}

The key value is required so it must be supplied. When the HasData method is used, EF Core will automatically generate SET IDENTITY INSERT ON for the relevant table, and the set it to OFF once the seeding has completed.

If you want to use the HasData method outside of a migration, you must call the Database.EnsureCreated() method, which you would normally do as part of a test, or in database initialisation code.

Data Annotations

There is no Data Annotation equivalent to the HasData method.

Last updated: 23/09/2018 19:30:12

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