EF中的transaction的使用范例

注意一点：

在EF中使用事物后，对于一个新增的model,在saveChanges后，可以得到该实体的自增ID，但在提交事物之前，

该数据并没有真正的新增到DB中，但此时可以得到model新增的自增ID，程序中可以使用，很方便！

例如下面的series实体在新增时，下面新增level时就可以直接使用，但此时的series并没有真正的新增到db中。

/// <summary>
        /// 导入汽车维护数据
        /// </summary>
        /// <param name="BrandName"></param>
        /// <returns></returns>
        public static Result ImportVehicleData(string strDataTable)
        {
            DataTable dt = JsonHelper.Deserialize<DataTable>(strDataTable);
            if (dt != null)
            {
                using (Entities db = new Entities())
                {
                    using (TransactionScope transaction = new TransactionScope())
                    {
                        try
                        {
                            var brandList = db.TL_Sys_VehicleBrand.ToList();
                            var seriesList = db.TL_Sys_VehicleSeries.ToList();
                            var levelList = db.TL_Sys_VehicleLevel.ToList();

                            string brandName = "";
                            string seriesName = "";
                            string levelName = "";
                            bool isInterest = true;
                            bool isDefault = true;

                            TL_Sys_VehicleBrand brand = new TL_Sys_VehicleBrand();
                            TL_Sys_VehicleSeries series = new TL_Sys_VehicleSeries();
                            bool isSave = false;
                            foreach (DataRow dr in dt.Rows)
                            {
                                brandName = dr[0].ToString().Trim();
                                isInterest = dr[3].ToString().Trim() == "否" ? false : true;
                                isDefault = dr[4].ToString().Trim() == "否" ? false : true;
                                brand = brandList.Where(p => p.Name == brandName).FirstOrDefault();

                                seriesName = dr[1].ToString().Trim();
                                series = seriesList.Where(p => p.CarBrandID == brand.ID && p.Name.Trim().Replace(" ", "") == seriesName.Trim().Replace(" ", "")).FirstOrDefault();
                                if (series == null)
                                {
                                    series = new TL_Sys_VehicleSeries();
                                    //新增车辆车系
                                    series.CarBrandID = brand.ID;
                                    series.Name = seriesName;
                                    series.Code = GetVehicleSeriesNextCode(brand, seriesList);
                                    series.IsInterest = isInterest;
                                    series.IsDefault = isDefault;
                                    db.TL_Sys_VehicleSeries.Add(series);
                                    db.SaveChanges();
                                    seriesList.Add(series);
                                }

                                levelName = dr[2].ToString().Trim();
                                if (!string.IsNullOrWhiteSpace(levelName) && series != null && series.ID > 0)
                                {
                                    var level = levelList.Where(p => p.CarLineID == series.ID && p.Name.Trim().Replace(" ", "") == levelName.Trim().Replace(" ", "")).FirstOrDefault();
                                    if (level == null)
                                    {
                                        level = new TL_Sys_VehicleLevel();
                                        //新增车辆车型
                                        level.CarLineID = series.ID;
                                        level.Name = levelName;
                                        level.Code = GetVehicleLevelNextCode(series, levelList);
                                        level.IsInterest = isInterest;
                                        level.IsDefault = isDefault;
                                        db.TL_Sys_VehicleLevel.Add(level);
                                        //db.SaveChanges();
                                        isSave = true;

                                        levelList.Add(level);
                                    }
                                }
                            }
                            //如果有新增的车型，就一起保存数据库
                            if (isSave)
                            {
                                db.SaveChanges();
                            }

                            transaction.Complete();
                            return new Result(true, "导入成功");
                        }
                        catch(Exception er)
                        {
                            transaction.Dispose();
                            return new Result(false, "导入发生异常，" + er.ToString());
                        }
                    }
                }
            }
            return new Result(false, "导入汽车信息不能为空");
        }