Question

我正在使用ASP.NET MVC和EF创建车辆预订应用程序，如果需要，用户可以在其中将多个车辆保留一个日期时间。我创建了一个存储过程，以防止车辆重复预订，但是在弄清楚如何将结果添加到列表中时遇到了麻烦。

示例：我想在2018年12月18日从12:00到13:00保留Vehicle＃1和Vehicle＃2 ....存储的过程转到db，以查找从中已保留Vehicle＃1 12:00至13:00，但不保留Vehicle＃2。由于foreach正在运行，alreadyReservedVehicle返回了.Count() = 0的结果，因为它看到了最后的结果，即没有保留Vehicle＃2。应该显示一条错误消息，说明不允许重复预订，因为Vehicle＃1已被预订，但未计入该预订。

是否有一种方法可以收集两个结果并告知应用程序，因为这2辆车中有一辆是保留的，所以都不能保留这辆车？

public ActionResult Create([Bind(Include = "ID,StartDate,EndDate,RequestorID,Destination,PurposeOfTrip,TransportStudentsFG,LastChangedBy,LastChangedDate,VehicleList,ThemeColor")] Reservations reservation)
{
    if (ModelState.IsValid)
    {
        var selectedVehicles = reservation.VehicleList.Where(x => x.IsChecked == true).ToList();
        List<usp_PreventDoubleBooking_Result> alreadyReservedVehicle = null;

        // get each vehicle that was selected to be reserved then check db to make sure it is available
        foreach (var selectedVehicle in selectedVehicles) 
        {             
            using (VehicleReservationEntities db = new VehicleReservationEntities())
            {
                alreadyReservedVehicle = db.usp_PreventDoubleBooking(selectedVehicle.ID, reservation.StartDate, reservation.EndDate).ToList();                             
            }
        }

        if (alreadyReservedVehicle.Count() == 0) // create a new reservation if the vehicle is available at the selected date and time
        {
            db.Reservations.Add(reservation);
            reservation.LastChangedDate = DateTime.Now;
            db.SaveChanges();
        }
        else
        {
            //return error message on page if vehicle is already reserved
            TempData["Error"] = "Double booking of vehicles is not allowed. Please choose another vehicle/time. Check the availability timeline before reserving to ensure there are no errors. Thank you.";
            return RedirectToAction("Create");
        }
    }
}

以上是我到目前为止所拥有的，并且我知道我已经接近了，因为假设用户仅尝试预订一辆已经预订的车辆，那么我所拥有的将起作用。当他们试图为多辆车创建预订时，代码仅计算列表中的最后一辆车，并以此作为确定是否保存预订的结果。

我曾考虑过将条件语句移到foreach中，但是我不希望为选择的每辆车都保存预订...这没有任何意义，因为只能保存1个预订，它只有多个可以关联的载具。

以下是查找预留车辆的存储过程：

SELECT 
    v.ID, r.StartDate, r.EndDate 
FROM 
    dbo.Reservations r
JOIN 
    dbo.ReservationToVehicle rtv ON r.id = rtv.ReservationID
JOIN 
    dbo.Vehicles v ON v.ID = rtv.VehicleID
WHERE
    (v.ID = @VehicleID)
    AND (r.StartDate <= @NewEndDate) 
    AND (r.EndDate >= @NewStartDate)

那么如何获取alreadyReservedVehicle List并将每个结果添加到列表中，以便确定List是否实际上具有Count为0？ >

更新：

这是存储过程的模型

public partial class usp_PreventDoubleBooking_Result
{
    public int ID { get; set; }
    public DateTime StartDate { get; set; }
    public DateTime EndDate { get; set; }
}

Answer 1

public ActionResult Create(/*Bind attribute omitted*/ Reservations reservation)
{
    if (ModelState.IsValid)
    {
        // Is 'IsChecked' nullable? If not, "== true" is redundant.
        var selectedVehicles = reservation.VehicleList.Where(x => x.IsChecked == true).ToList();

        // get each vehicle that was selected to be reserved then check db to make sure it is available
        using (VehicleReservationEntities db = new VehicleReservationEntities())
        {
            foreach (var selectedVehicle in selectedVehicles)
            {
                // 'alreadyReservedVehicle' can be declared here because you don't need to let it
                // out of its cage, I mean the loop.
                List<usp_PreventDoubleBooking_Result> alreadyReservedVehicle =
                    db.usp_PreventDoubleBooking(selectedVehicle.ID, reservation.StartDate, reservation.EndDate).ToList();

                if (alreadyReservedVehicle.Count() > 0)
                {
                    //return error message on page if vehicle is already reserved
                    TempData["Error"] = "Double booking of vehicles is not allowed. Please choose another vehicle/time. Check the availability timeline before reserving to ensure there are no errors. Thank you.";
                    return RedirectToAction("Create");
                }
            }
        }

        // create a new reservation if the vehicle is available at the selected date and time
        db.Reservations.Add(reservation);
        reservation.LastChangedDate = DateTime.Now;
        db.SaveChanges();
    }
}

Answer 2

您可以执行以下操作：

var preventDoubleBookingList= await context.Database.SqlQuery<usp_PreventDoubleBooking>("sproc_name", prams_here).ToListAsync();

您将必须创建一个与存储过程匹配的模型。

如何从存储过程结果实体框架中创建列表

2 个答案: