c# – 从EF中的集合中删除项目 – 奇怪的问题

我正在使用一个实体框架项目,我正在努力从我的一个集合中删除一个Item.
我首先通过以下方式在我的对象“Resto”和“OpeningTimes”之间创建了“一对多”关系：
在我的模型中：

[Table("Resto")]
public class Resto
{
    public int Id { get; set; }
    public string Name { get; set; }
    public string PhoneNumber { get; set; }
    public string Address { get; set; }   //TODO Ajouter adresse détaillées 

    public virtual ICollection<SlotTime> OpeningTimes {get; set;}




    public virtual ICollection<ApplicationUser> Administrators { get; set; }
    public virtual ICollection<ApplicationUser> Chefs { get; set; }

    public virtual Menu Menu {get; set;}
}
[Table("RestoSlotTimes")]

public class SlotTime
{
    public int SlotTimeId { get; set; }
    public DayOfWeek DayOfWeek { get; set; }
    public TimeSpan OpenTime { get; set; }
    public TimeSpan CloseTime { get; set; }


    public int RestoId { get; set; }
    public virtual Resto Resto { get; set; }
}

由于我有来自该对象的其他关系(请参阅应用程序用户中的那个),我也使用Fluent语言来消除歧义.

方式如下：

modelBuilder.Entity<Resto>()
                    .HasMany<ApplicationUser>(s => s.Administrators)
                    .WithMany(c => c.Resto_Admin)
                    .Map(cs =>
                    {
                        cs.MapLeftKey("Resto_Admin");
                        cs.MapRightKey("Admin");
                        cs.ToTable("RestosAdmins");
                    });

        modelBuilder.Entity<Resto>()
        .HasMany<ApplicationUser>(s => s.Chefs)
        .WithMany(c => c.Resto_Chefs)
        .Map(cs =>
        {
            cs.MapLeftKey("Resto_Chefs");
            cs.MapRightKey("Chef");
            cs.ToTable("RestosChefs");
        });
modelBuilder.Entity<Resto>()
                    .HasOptional(s => s.Menu) 
                    .WithRequired(ad => ad.resto)
                    .WillCascadeOnDelete(true);

但这些关系工作正常.

今天我在我的控制器中对我的“OpeningTimes”进行基本操作,因为在DB中添加了以下项目：

[HttpPost]
    public async Task<ActionResult> AddSlotTimeToRestaurant(AddSlotTimeToRestaurantView model)
    {
        var resto = await DbManager.Restos.FirstAsync(r => r.Id == model.RestoId);
        if(resto != null)
        {
            if(model.OpenTimeId < model.CloseTimeId)
            {
                SlotTime slotTime = new SlotTime()
                {
                    DayOfWeek = model.Day,
                    OpenTime = model.SlotTimeList.timeSpanViews.FirstOrDefault(m => m.Id == model.OpenTimeId).TimeSpan,
                    CloseTime = model.SlotTimeList.timeSpanViews.FirstOrDefault(m => m.Id == model.CloseTimeId).TimeSpan
                };
                resto.OpeningTimes.Add(slotTime);
                await DbManager.SaveChangesAsync();
                return RedirectToAction("edit", new { id = model.RestoId });
            }
            else
            {
                ModelState.AddModelError("SelectedSlotTimeId_1_Stop", "L'heure de fermeture doit être après l'heure d'ouverture");
                return View();
            }               
        }
        return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
    }

此代码按预期工作.
但现在我尝试使用以下代码执行另一个删除对象的功能：

public async Task<ActionResult> RemoveSlotTimeToRestaurant(int RestoId, int SlotId)
    {
        var resto = await DbManager.Restos.FirstAsync(r => r.Id == RestoId);
        if (resto != null)
        {
            SlotTime slotTime = resto.OpeningTimes.FirstOrDefault(m => m.SlotTimeId == SlotId);

            if(slotTime != null)
            {
                resto.OpeningTimes.Remove(slotTime);
                await DbManager.SaveChangesAsync();
                return RedirectToAction("edit", new { id = RestoId });
            }
        }
        return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
    }

我在DbSave线上有一个错误……看起来它看起来像EF试图不删除我的对象而只是保留它并将其ID设置为Null …这不是我所期望的

The operation failed: The relationship could not be changed because one or more of the foreign-key properties is non-nullable. When a change is made to a relationship, the related foreign-key property is set to a null value. If the foreign-key does not support null values, a new relationship must be defined, the foreign-key property must be assigned another non-null value, or the unrelated object must be deleted

我觉得我的关系配置好EF.我觉得要正确地添加和删除关系……
你认为这可以来自流畅的配置吗？

BTW一旦我删除了“Resto”,我的级联删除工作得很好,我的所有项目“OpeningTimes”都被很好地删除了DB而没有错误.

最好的祝福,

如果您希望能够通过父实体(Resto)修改子实体(OpeningTimes),则需要在模型构建器中指定两者之间的关系：

modelBuilder.Entity<Resto>()
    .HasMany(r => r.OpeningTimes) 
    .WithOptional()
    .HasForeignKey(ot => ot.RestoId)

This blog post详细介绍了处理这种情况.

另一种方法是直接从DbContext上定义的DbSet中删除实体：

DbManager.SlotTimes.Remove(slotTime);