实体框架只保存最后一行（主数据） [英] Entity Framework only saving last row (master details)

问题描述

我的项目是c＃Windows应用程序，我正在使用实体框架5和.net 4.5。

我有房间和床模块，您可以添加，编辑和删除房间和/或床位在我的窗体上我有一个RoomNo和Station的字段，还有添加和删除按钮添加/删除床（s） ）to datagridview

  DB结构
 
房间（表）
 PK_Rooms 
 FK_Station 
 RoomNo 
 
床（桌）
 PK_Beds 
 FK_Rooms 
 BedNo 
 FullRoomNo（仅限Roomno和Bedno）
 RoomStatus 
  

下面是我的添加方法来添加房间和床到DB

  M3dEntities m3d = new M3dEntities（）; 
 rooms rooms =新房（）; 
床位=新床（）; 
 
 string RoomNo = RoomNoTxt.Text; 
 int StationID = Int32.Parse（StationCmb.SelectedValue.ToString（））; 
 
 var roomnoexist = from g in m3d.rooms 
其中g.RoomNo == RoomNo 
 select g; 
 
 if（roomnoexist.Any（））
 {
 MessageBox.Show（Room No. Already Exist！）; 
} 
 else 
 {
 rooms.RoomNo = RoomNo; 
 rooms.FK_Stations = StationID; 
 
 m3d.rooms.AddObject（rooms）; 
} 
 
 foreach（BedsDataGridView.Rows中的DataGridViewRow行）
 {
 beds.Bedno = row.Cells [0] .Value.ToString（）; 
 beds.FullRoomNo = row.Cells [1] .Value.ToString（）; 
 beds.RoomStatus =可用; 
 m3d.beds.AddObject（床）; 
} 
 
 m3d.SaveChanges（）; 
  

（例如：添加房间1201，带4张床）
只剩下最后一张床到DB。

我的问题：

1. 为什么只保存最后一行？


2. 如何将所有行保存到床上？


3. 如何使用编辑方法（在当前房间添加另一张床或删除床）？

解决方案

您应该移动床位=新床（）; 在 foreach 中的说明如下：

 code> foreach（BedsDataGridView.Rows中的DataGridViewRow行）
 {
床位=新床（）; //这是它的地方。 
 beds.Bedno = row.Cells [0] .Value.ToString（）; 
 beds.FullRoomNo = row.Cells [1] .Value.ToString（）; 
 beds.RoomStatus =可用; 
 m3d.beds.AddObject（床）; 
} 
  

Wihtout你总是在最后一个 其中最后一行包含最后一行，并只保存该行。

旁注：以获得某些性能如果您正在插入多个对象，请使用 AddRange

  var bedsCollection = new List< beds>（）; 
 foreach（BedsDataGridView.Rows中的DataGridViewRow行）
 {
床位=新床（）; //这是它的地方。 
 beds.Bedno = row.Cells [0] .Value.ToString（）; 
 beds.FullRoomNo = row.Cells [1] .Value.ToString（）; 
 beds.RoomStatus =可用; 
 bedsCollection.Add（beds）; //更新集合而不是DbSet 
} 
 
 m3d.beds.AddRange（bedsCollection）; 
 m3d.SaveChanges（）; 
  

My project is c# Windows Application, I am using Entity Framework 5 and .net 4.5.

I have Rooms and Beds module which you can add, edit and delete Room(s) and/or bed(s)

on my Form I have a field for RoomNo and Station, also Add and Delete button to add/delete bed(s) to datagridview

DB Structure

Rooms (table)
PK_Rooms
FK_Station
RoomNo

Beds (table)
PK_Beds
FK_Rooms
BedNo
FullRoomNo (concat only of Roomno and Bedno)
RoomStatus

below is my Add Method to add the room and beds to DB

M3dEntities m3d = new M3dEntities();
rooms rooms = new rooms();
beds beds = new beds();

string RoomNo = RoomNoTxt.Text;
        int  StationID = Int32.Parse(StationCmb.SelectedValue.ToString());

        var roomnoexist = from g in m3d.rooms
                          where g.RoomNo == RoomNo
                          select g;

        if (roomnoexist.Any())
        {
            MessageBox.Show("Room No. Already Exist!");
        }
        else
        {
            rooms.RoomNo = RoomNo;
            rooms.FK_Stations = StationID;

            m3d.rooms.AddObject(rooms);
        }

        foreach (DataGridViewRow row in BedsDataGridView.Rows)
        {
            beds.Bedno = row.Cells[0].Value.ToString();
            beds.FullRoomNo = row.Cells[1].Value.ToString();
            beds.RoomStatus = "Available";
            m3d.beds.AddObject(beds);
        }

        m3d.SaveChanges();

(Ex: add room 1201 with 4 beds) Only last row of bed is saved to DB.

My Questions:

1. Why only save the last row?
2. How to save all rows to beds?
3. How can i do it for Edit Method (To add another bed or delete bed on the current room)?

解决方案

You should move the beds beds = new beds(); instruction inside your foreach statement like this:

foreach (DataGridViewRow row in BedsDataGridView.Rows)
{
     beds beds = new beds(); // Here is its place.
     beds.Bedno = row.Cells[0].Value.ToString();
     beds.FullRoomNo = row.Cells[1].Value.ToString();
     beds.RoomStatus = "Available";
     m3d.beds.AddObject(beds);
}

Wihtout that you are always oiverriden the last instance of beds which end up containing your last row and save only that row.

Side note: to gain some performance use AddRange if you are inserting multiple objects once like this:

var bedsCollection = new List<beds>();
foreach (DataGridViewRow row in BedsDataGridView.Rows)
{
     beds beds = new beds(); // Here is its place.
     beds.Bedno = row.Cells[0].Value.ToString();
     beds.FullRoomNo = row.Cells[1].Value.ToString();
     beds.RoomStatus = "Available";
     bedsCollection.Add(beds); // update the collection not the DbSet
}

m3d.beds.AddRange(bedsCollection);
m3d.SaveChanges();

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