EF upsert必须手动完成吗？

Question

我想要插入现有实体的引用成员.

我是否必须为upsert编写特定代码？

意思是:我必须检查我是在处理现有的参考成员还是新成员.

还有其他简单的方法吗？

你这样做会发生什么Save？

  public void SaveCofiguration(MamConfiguration_V1Ui itemUi)
        {
            var itemEf = mMamConfiguration_V1UiToEfConvertor.ConvertToNewEf(itemUi);

            using (var maMDBEntities = new MaMDBEntities())
            {
                IDal<MamConfiguration_V1> mamConfigurationDal = mDalFactory.GetDal<MamConfiguration_V1>(maMDBEntities);

                mamConfigurationDal.Save(itemEf);
            }
        }

         public MamConfiguration_V1 GetById(object id)
        {           
                id.ThrowIfNull("id");

                int configurationId = Convert.ToInt32(id);

                var result =
                    mMaMDBEntities.MamConfiguration_V1.SingleOrDefault(item => item.ConfigurationId == configurationId);

                return result;

        }

       public MamConfiguration_V1 Save(MamConfiguration_V1 item)
        {

                item.ThrowIfNull("item");

                var itemFromDB = GetById(item.ConfigurationId);

                if (itemFromDB != null)
                {
                    UpdateEfItem(itemFromDB, item);

                   // if (mMaMDBEntities.ObjectStateManager.GetObjectStateEntry(itemFromDB).State == EntityState.Detached)
//                    {
  //                      mMaMDBEntities.MamConfiguration_V1.AddObject(itemFromDB);
    //                }

                    // Attached object tracks modifications automatically
                    mMaMDBEntities.SaveChanges();

                    return item;
                }





       private void UpdateEfItem(MamConfiguration_V1 itemFromDb, MamConfiguration_V1 itemFromUi)
            {
                itemFromDb.UpdatedDate = DateTime.Now;

                itemFromDb.Description = itemFromUi.Description;

                itemFromDb.StatusId = itemFromUi.StatusId;

                itemFromDb.Name = itemFromUi.Name;

                itemFromDb.NumericTraffic = itemFromUi.NumericTraffic;

                itemFromDb.PercentageTraffic = itemFromUi.PercentageTraffic;

                itemFromDb.Type = itemFromUi.NumericTraffic;

                foreach (var item in itemFromDb.MamConfigurationToBrowser_V1.ToList())
                {
                    if (itemFromUi.MamConfigurationToBrowser_V1.All(b => b.BrowserVersionId != item.BrowserVersionId))
                    {
                        mMaMDBEntities.MamConfigurationToBrowser_V1.DeleteObject(item);
                    }
                }

                for (int i = 0; i < itemFromUi.MamConfigurationToBrowser_V1.Count; i++)
                {
                    var element = itemFromUi.MamConfigurationToBrowser_V1.ElementAt(i);
                    var item = itemFromDb.MamConfigurationToBrowser_V1.SingleOrDefault(b => b.BrowserVersionId == element.BrowserVersionId);
                    if (item != null)
                    {
                        // copy properties from element to item
                    }
                    else
                    {
                        element.Browser = mMaMDBEntities.Browsers.Single(browserItem =>
                            browserItem.BrowserID == element.BrowserID);

                        //element.MamConfiguration_V1 = itemFromDb;

                        //have also tried: element.MamConfiguration_V1 = null;

                        //element.MamConfiguration_V1Reference = null;

                        itemFromDb.MamConfigurationToBrowser_V1.Add(element);
                    }
                }
            }

但我会预料到Save(itemUi)并且SaveChanges()工作正常.没有？

Answer 1

public void InsertOrUpdate(DbContext context, UEntity entity)
{
    context.Entry(entity).State = entity.Id == 0 ?
                                   EntityState.Added :
                                   EntityState.Modified;
    context.SaveChanges();
}

http://forums.asp.net/t/1889944.aspx/1

Answer 2

为了避免查询然后插入或抛出异常的开销，您可以利用对合并或更新插入的底层数据库支持。

这个 nuget 包可以很好地完成这项工作：https ://www.nuget.org/packages/FlexLabs.EntityFrameworkCore.Upsert/

Github：https : //github.com/artiomchi/FlexLabs.Upsert

例子：

DataContext.DailyVisits
    .Upsert(new DailyVisit
    {
        // new entity path
        UserID = userID,
        Date = DateTime.UtcNow.Date,
        Visits = 1,
    })
    // duplicate checking fields
    .On(v => new { v.UserID, v.Date })
    .WhenMatched((old, @new) => new DailyVisit
    {
        // merge / upsert path
        Visits = old.Visits + 1,
    })
    .RunAsync();

底层生成的 sql 执行正确的 upsert。此命令会立即运行并且不使用更改跟踪，因此这是一个限制。