定石1: ADO.NETをそのまま使う最小コード

// ✅定石1: ADO.NET最小コード（ControllerのAction内で使う）
public class CustomerController : Controller
{
    public ActionResult Index()
    {
        var customers = new List<CustomerVm>();
 
        using (var conn = new SqlConnection(ConfigurationManager.ConnectionStrings["MyDb"].ConnectionString))
        using (var cmd = new SqlCommand("SELECT id, name FROM customers WHERE status = @s", conn))
        {
            cmd.Parameters.AddWithValue("@s", "active");
            conn.Open();
 
            using (var reader = cmd.ExecuteReader())
            {
                while (reader.Read())
                {
                    customers.Add(new CustomerVm
                    {
                        Id = reader.GetInt32(0),
                        Name = reader.GetString(1),
                    });
                }
            }
        }
        return View(customers);
    }
}