从 Entityframework 将 Identity 值映射到 DTO答案

【问题标题】：Mapping Identity value into DTO from Entityframework从 Entityframework 将 Identity 值映射到 DTO
【发布时间】：2015-07-29 18:15:14
【问题描述】：

我有从我的 DTOCollection 进行批量插入的方法，它有 3 级循环。

public List<FirstCollectionDTO> BulkInsert(List<FirstCollectionDTO> collection)
    {
        using (var db = new DemoEntities())
        {
            //Setting Auto Detech Changes false when starting loop
            db.Configuration.AutoDetectChangesEnabled = false;

            //Looping start
            collection.ForEach(myitem =>
                {
                    myitem.SecondCollection.ForEach(secondLevel =>
                        {
                                 //Some Operation Over here


                            secondLevel.ThirdCollection.ForEach(thirdItem =>
                                {
                                    var myEntity= new MyTable()
                                    {
                                        Level=thirdItem.Name,
                                        Method=thirdItem.Method,
                                      Representation=thirdItem.Representation,
                                    };

                                    var insertedItem = db.MyTable.Add(myEntity);

                                    //Setting the reference of id to the 
                                    //DTO after the save changes. 
                                    //This seems always 0 as it this time
                                    // it have no id only after save changes the id be passed into InsertedItem , I have to pass the reference to myDTO also
                                    thirdItem.Id = insertedItem.Id;
                                });
                        });
                });

            //Setting Auto Detech Changes true when starting loop
            db.Configuration.AutoDetectChangesEnabled = true;

            // Here I save my changes
            db.SaveChanges();

            return collection;
        }
    }

如果 INSERT 操作成功，服务器生成的值将被写回。那么我如何将这个值也放入我的 DTO 中。

保存更改后如何获取插入对象的 Id，我需要维护 3 级集合的关系，即使

【问题讨论】：

值在SaveChanges 期间被分配并读回实体，因此在此之前您无法知道它们。
@GertArnold 有什么办法可以在保存更改后获取 id 并保持 3 个级别的关系。
thirdItem 可以有一个属性MyTable，包含实体对象，所以thirdItem.Id 可以返回实体的ID。
@GertArnold, ThirdItem 是 DTO 对象，我希望避免从 DTO 引用 EF
然后在此过程中使用接口（用于 EF 类）或构建 DTO/Entity 对的字典。

标签： c# entity-framework orm pass-by-value

【解决方案1】：

//To get the inserted id 
var anonymousprojectList = (new[] { new { FirstCollectionId= 0, SecondCollectionId= 0, ThirdObject= new Document() } }).ToList();


using (var db = new DemoEntities())
    {
        //Setting Auto Detech Changes false when starting loop
        db.Configuration.AutoDetectChangesEnabled = false;

        //Looping start
        collection.ForEach(myitem =>
            {
                myitem.SecondCollection.ForEach(secondLevel =>
                    {
                             //Some Operation Over here


                        secondLevel.ThirdCollection.ForEach(thirdItem =>
                            {
                                var myEntity= new MyTable()
                                {
                                    Level=thirdItem.Name,
                                    Method=thirdItem.Method,
                                  Representation=thirdItem.Representation,
                                };

                                var insertedItem = db.MyTable.Add(myEntity);

                                //Setting the reference of id to the 
                                //DTO after the save changes. 
                                //This seems always 0 as it this time
                                // it have no id only after save changes the id be passed into InsertedItem , I have to pass the reference to myDTO also
                                using (var db = new DemoEntities())
    {
        //Setting Auto Detech Changes false when starting loop
        db.Configuration.AutoDetectChangesEnabled = false;

        //Looping start
        collection.ForEach(myitem =>
            {
                myitem.SecondCollection.ForEach(secondLevel =>
                    {
                             //Some Operation Over here


                        secondLevel.ThirdCollection.ForEach(thirdItem =>
                            {
                                var myEntity= new MyTable()
                                {
                                    Level=thirdItem.Name,
                                    Method=thirdItem.Method,
                                  Representation=thirdItem.Representation,
                                };

                                var insertedItem = db.MyTable.Add(myEntity);

                                //Setting the reference of id to the 
                                //DTO after the save changes. 
                                //This seems always 0 as it this time
                                // it have no id only after save changes the id be passed into InsertedItem , I have to pass the reference to myDTO also
                                anonymousprojectList.Add(new {FirstCollectionID = myItem.Od,SecondCollectionId=secondLevel.Id,ThirdObject = insertedItem});
                            });
                    });
            });

        //Setting Auto Detech Changes true when starting loop
        db.Configuration.AutoDetectChangesEnabled = true;

        // Here I save my changes
        db.SaveChanges();

                            });
                    });
            });

        //Setting Auto Detech Changes true when starting loop
        db.Configuration.AutoDetectChangesEnabled = true;

        // Here I save my changes
        db.SaveChanges();
   }
       // Loop through the anonymous collection and assign to the input collection itself 
       //Skip header item
       anonymousprojectList.Skip(1).ToList().ForEach(object=>
        {
          //Loop through the three level and assign the value

          //Assign the value
          ThirdlevelItem.Id = ThirdObject.Id) 

        });

return collection

【讨论】：