asp.net - 在多对多关系表中插入和删除值

Question

我想将值插入到我正在使用实体框架和 linq 的多对多关系表中。我想建立插入查询（.net Framework 4）

以下是表格

菜单 - menu_id、menu_name、menu_desc

迎合 - cater_id、cater_name、enable_ind

关系表 Menu_Cater - menu_id、cater_id

如果有实现此插入和删除的简单方法，我尝试过几种情况似乎不起作用

Answer 1

我不知道，如果你现在需要它，但我会告诉你怎么做。如果我没听错的话，你的意思就是那样。

public ActionResult Create(Cater cater, int menuId)
{
    //Find menu with our menu_id
    Menu menu = db.Menus.Where(m => m.menu_id == menuId).FirstOrDefault();

    //Add cater for this Menu
    menu.Cater.Add(cater);
    db.SaveChanges();

    return somethere...
}

public ActionResult Remove(int caterId, int menuId)
{
 //Choose menu, from him we will delete cater which we need 
 Menu menu = db.Menus.Where(m => m.menu_id == menuId).FirstOrDefault();

 //Find cater which we want delete from this Menu
 Cater cater = menu.Cater.Where(c => c.cater_id == caterId).FirstOrDefault();

 //Remove him from Table Menu_Cater
 menu.Cater.Remove(cater);
 db.SaveChanges();

 return somethere...
}

就这样。它对 MVC4 的工作

Answer 2

假设您有MenuandCater对象（来自下拉列表或但是），只需：

1. 创建Menu_Cater记录
2. 将其设置为在提交时插入
3. 提交更改

如下所示：

VB.NET

Dim menu As Menu = GetSelectedMenu() ' However you get the Menu record
Dim cater As Cater = GetSelectedCater() ' However you get the Cater record

Dim relationship = New Menu_Cater()
' EITHER:
relationship.menu_id = menu.menu_id
relationship.cater_id = cater.cater_id
' OR:
' relationship.menu = menu
' relationship.cater = cater

Using db = new MyDataContext
    db.Menu_Cater.InsertOnSubmit( relationship )
    db.SubmitChanges()
End Using

C＃

Menu menu = GetSelectedMenu(); // However you get the Menu record
Cater cater = GetSelectedCater(); // However you get the Cater record

Menu_Cater relationship = new Menu_Cater();
// EITHER:
relationship.menu_id = menu.menu_id;
relationship.cater_id = cater.cater_id;
// OR:
// relationship.menu = menu
// relationship.cater = cater

using (db = new MyDataContext()) {
    db.Menu_Cater.InsertOnSubmit(relationship);
    db.SubmitChanges();
}

可能需要对您的变量/数据库字段名称进行小的更改。也许db.Save()不是db.SubmitChanges()取决于数据上下文的类型。