Question

我有一个数据库表：

Item{ItemId ...}
Item{BoardId ...}
ItemsInBoards{ItemId, BoardId, CreatedOnDate}

我的应用程序中有模型

public class Item
{
public int ItemId{get;set;}
...
public virtual ICollection<Board> Boards { get; set; }
}

public class Board
{
public int BoardId{get;set;}
...
public virtual ICollection<Item> Items { get; set; }
}

保存...

...
Item item = con.Item.Find(model.ItemId); // Find item by ID
// Try to save
Board b = con.Boards.Find(model.BoardId); // Find a board by ID
                b.CreatedOnDate = DateTime.Now; // This is the issue
                item.Boards.Add(b);
                con.SaveChanges();

它已保存但没有CreatedOnDate。我不知道如何设置CreatedOnDAte字段以将其保存在数据库中。

Answer 1

这不是多对多的关系。您需要两个一对多关系，并且必须将ItemsInBoards公开为模型实体：

public class Item
{
    public int ItemId{get;set;}
    ...
    public virtual ICollection<ItemInBoard> ItemsInBoard { get; set; }
}

public class Board
{
    public int BoardId{get;set;}
    ...
    public virtual ICollection<ItemInBoard> ItemsInBoard { get; set; }
}

public class ItemInBoard
{
    [Key, Column(Order = 1)]
    public int ItemId{get;set;}
    [Key, Column(Order = 2)]
    public int BoardId{get;set;}

    public DateTime CreatedOnDate{get;set;}

    public virtual Item Item{get;set;}
    public virtual Board Board{get;set;}
}

然后您可以通过以下方式写入关联表 - 包括CreatedOnDate属性值 -

var newItemInBoard = new ItemInBoard
{
    ItemId = model.ItemId,
    BoardId = model.BoardId,
    CreatedOnDate = DateTime.Now
};
con.ItemsInBoard.Add(newItemInBoard);
con.SaveChanges();

有关此类型号的更多详情，请访问：https://stackoverflow.com/a/7053393/270591

EF多对多保存问题

1 个答案: