Seeding data with EF Core 2.1

BooksContext.cs

public class BooksContext : DbContext
{
    private const string ConnectionString = @"server=(localdb)\MSSQLLocalDb;database=Books1;trusted_connection=true";
    public DbSet<Book> Books { get; set; }
    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        base.OnConfiguring(optionsBuilder);
        optionsBuilder.UseSqlServer(ConnectionString)
               .ConfigureWarnings(warnings => warnings.Throw(RelationalEventId.QueryClientEvaluationWarning));
    }

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        base.OnModelCreating(modelBuilder);

        modelBuilder.Entity<Book>().Property(b => b.Title)
            .IsRequired()
            .HasMaxLength(50);
        modelBuilder.Entity<Book>().Property(b => b.Publisher)
            .IsRequired(false)
            .HasMaxLength(30);

        modelBuilder.Entity<Book>().HasData(
            new Book { BookId = 1, Title = "Professional C# 6", Publisher = "Wrox Press"},
            new Book { BookId = 2, Title = "Professional C# 7", Publisher = "Wrox Press"},
            new Book { BookId = 3, Title = "Professional C# 8", Publisher = "Wrox Press"}
        );
    }
}