using Microsoft.EntityFrameworkCore;
public sealed class LabDb : DbContext
{
    public LabDb(DbContextOptions<LabDb> options) : base(options) { }
    public DbSet<Item> Items => Set<Item>();
    protected override void OnModelCreating(ModelBuilder model)
    {
        model.Entity<Item>().HasIndex(x => new { x.SortKey, x.Id });
    }
}
public sealed class Item
{
    public int Id { get; set; }
    public int SortKey { get; set; }
    public string Name { get; set; } = "";
}