Question

我已经查看并找不到什么接缝是一个简单的事情的解决方案，我有3个实体当我尝试删除城市或区我得到这个例外：

System.Data.Entity.Infrastructure.DbUpdateException: An error occurred while updating the entries. See the inner exception for details. ---> System.Data.Entity.Core.UpdateException: An error occurred while updating the entries. See the inner exception for details. ---> System.Data.SqlServerCe.SqlCeException: The primary key value cannot be deleted because references to this key still exist. [ Foreign key constraint name = FK_dbo.User_dbo.District_DistrictId ]

我想要达到的目标是：当我删除一个城市时，所有儿童区都要删除，而不是用户。当我删除一个区时，只删除该区。当我删除用户时，仅删除用户。

市
- 一个城市可以拥有0-N个区域并将删除级联
区
- 区域必须拥有城市并且具有可选的0 - N个用户
用户
- 用户可以选择0 - 1区

实体用户

public class User
{
  public Guid UserId { get; set; }

  public virtual District District { get; set; }
  public Guid? DistrictId { get; set; }
 }

实体城市

public class City 
{
    public Guid CityId { get; set; }

    public virtual ICollection<District> Districts { get; set; }
}

实体区

public class District 
{
    public Guid DistrictId { get; set; }

    public City City { get; set; }
    public Guid CityId { get; set; }

    public virtual ICollection<User> Users { get; set; }
}
//EntityTypeConfiguration
   HasRequired(d => d.City)
            .WithMany(c => c.Districts)
            .HasForeignKey(d => d.CityId)
            .WillCascadeOnDelete(true); 

    HasMany(d=> d.Users)
            .WithOptional(u=> u.District)
            .HasForeignKey(u=> u.DistrictId)
            .WillCascadeOnDelete(false);

我尝试在用户映射中放置此配置，但没有任何更改相同的错误

HasOptional(u => u.District)
            .WithMany(d => d.Users)
            .HasForeignKey(u => u.DistrictId)
            .WillCascadeOnDelete(false);

我也在使用Sqlce4和EF6以及Generic Unit of Work & Repositories Framework

感谢您的帮助

此致

Answer 1

您必须将DistrictId的{{1}}外键设置为User，以避免在尝试删除null或{时违反约束条件{1}}。如果相关的City未加载到上下文中，EF将不会自动执行此操作。

要删除区域，您可以这样做：

District

删除城市：

Users

Cacsading delete会关注在这里删除这些区域。但是，我不确定在这种情况下，加载用户的// "Include" because you need the users to nullify their FKs to the district var district = context.Districts.Include(d => d.Users) .SingleOrDefault(d => d.DistrictId == someDistrictId); if (district != null) { // "Remove" will set the FKs of the LOADED users to null context.Districts.Remove(district); context.SaveChanges(); }是否会设置为var city = context.Cities.Include(c => c.Districts.Select(d => d.Users)) .SingleOrDefault(c => c.CityId == someCityId); if (city != null) { context.Cities.Remove(city); context.SaveChanges(); }。如果它不起作用，你必须手动完成：

DistrictId

Answer 2

谢谢大家，以为EF足够聪明，可以处理像这样的简单任务。所以不仅要清除区域，不仅仅是城市，这里是我最终使用这个存储库来工作的方式

  var city = _unitOfWork.Repository<City>().Query()
            .Include(c => c.Districts.Select(d => d.Users))
            .Filter(c => c.CityName.Equals(cityName, StringComparison.InvariantCultureIgnoreCase))
            .Get().FirstOrDefault();

        if (city != null)
        {
            var districts = city.Districts.ToList();
            for (var i = districts.Count - 1; i >= 0; i--)
            {
                var users = districts[i].Users.ToList();
                for (var j = users.Count - 1; j >= 0; j--)
                {
                    users[j].DistrictId = null;
                    users[j].ObjectState = ObjectState.Modified;

                    _unitOfWork.Repository<User>().Update(users[j]);
                }
                districts[i].Users.Clear();
                _unitOfWork.Repository<District>().Delete(districts[i]);
            }
            _unitOfWork.Repository<City>().Delete(city);

很糟糕但是很有效

ef-Code-First一对多可选删除抛出异常：无法删除主键值

2 个答案: