Entity Framework 6：删除多个父项的子项

Question

请帮忙。我和 EntityFramework 一起工作 6. 有实体：

public class PowerStation {

        public Guid PowerStationId { get; set; }
        public string Name { get; set; }

        public Guid PowerStationTypeId { get; set; }
        public virtual PowerStationType PowerStationType { get; set; }

        public Guid SubjectId { get; set; }
        public DateTime SubjectTransactionTime { get; set; }
        public virtual Subject Subject { get; set; }

        public Guid ParticipantOremId { get; set; }
        public DateTime ParticipantOremTransactionTime { get; set; }
        public virtual ParticipantOrem ParticipantOrem { get; set; }

        public Guid? DcId { get; set; }
        public DateTime? DcTransactionTime { get; set; }
        public virtual Dc Dc { get; set; }

        public virtual ICollection<Equipment> Equipments { get; set; }
        public virtual ICollection<DcLink> DcLinks { get; set; }   
        public virtual ICollection<DcPowerStationProposal> DcPowerStationProposals { get; set; }
}

我尝试删除这个实体，但出现异常：

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.

我可以试试这个：

entity = db.PowerStations
                    .Include(x => x.Equipments)
                    .Include(x => x.DcLinks)
                    .Include(x => x.DcPowerStationProposals)
                    .FirstOrDefault(x => x.PowerStationId == entity.PowerStationId && x.TransactionTime == entity.TransactionTime);


var station = db.ParticipantOrems.FirstOrDefault(x => x.ParticipantOremId == entity.ParticipantOremId
                && x.TransactionTime == entity.ParticipantOremTransactionTime);
                station.PowerStations.Remove(entity);

var subject = db.Subjects.FirstOrDefault(x => x.SubjectId == entity.SubjectId
                && x.TransactionTime == entity.SubjectTransactionTime);
                subject.PowerStations.Remove(entity);

var dc = db.Dcs.FirstOrDefault(x => x.DcId == entity.DcId
                && x.TransactionTime == entity.DcTransactionTime);
                dc.PowerStations.Remove(entity);

var type = db.PowerStationTypes.FirstOrDefault(x => x.PowerStationTypeId == entity.PowerStationTypeId);
                type.PowerStations.Remove(entity);

db.Equipments.Local.Where(x => x.PowerStation == null).ToList().ForEach(r => Equipments.Remove(r));
db.DcLinks.Local.Where(x => x.PowerStation == null).ToList().ForEach(r => DcLinks.Remove(r));
db.PowerStationProposals.Where(x => x.PowerStation == null).ToList().ForEach(r => DcPowerStationProposals.Remove(r));

Answer 1

如果您想删除整个 PowerStation，您应该删除迁移并重新更新它

Entity Framework 6：删除多个父项的子项

Entity Framework 6: Delete Child item for several parent

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