实体框架将记录到多对多的映射表 [英] Entity Framework adding record into many to many mapping table

问题描述

我有3个表，

1），客户（编号，名称，BLA BLA） 2）CustomerGroups（GroupId的，组名） 3）CustomerInGroups（客户ID，的GroupId）

1) Customer (Id, Name, bla bla) 2) CustomerGroups (GroupId, GroupName) 3) CustomerInGroups (CustomerId, GroupId)

using (var context = DataObjectFactory.CreateContext())
{                
    context.Customers.Add(entity);
    context.SaveChanges();
    return entity.Id;
}

我如何添加一条记录CustomerInGroups？的EntityFramework不会产生这样的许多一对多映射表实体

How do I add a record into CustomerInGroups? EntityFramework doesn't generate entities for such many-to-many mapping tables

编辑：

无论是在客户和CustomerGroups的Id列设置为自动递增。

Both the Id columns in Customer and CustomerGroups are set to auto increment.

所以在我CustomersGroup表，我有

So in my CustomersGroup table, I have

Id          Name
----------------------------
1           Normal
2           VIP

我想这样做，作为海报的一个建议：

I tried doing this as one of the posters suggested:

entity.CustomerGroups = new List<CustomerGroup>
{
    new CustomerGroup {Id = 2 }
};
context.Customers.Add(entity);
context.SaveChanges();
return entity.Id;

然而，当我这样做，而不是创建一个记录在映射表是这样的：

However, when I did this, instead of creating a record in the mapping table like this:

CustomerId          GroupId
----------------------------
1                   2

我得到的是

CustomerInGroups
    CustomerId          GroupId
    ----------------------------
    1                   3

CustomerGroups
    Id          Name
    ----------------------------
    1           Normal
    2           VIP
    3           NULL

它实际上创造了我CustomerGroups表中的另一个入口，这是不是我想要的。

It actually created another entry in my CustomerGroups table, which is not what I want

推荐答案

飞有点盲目的因为你没有包含什么样的属性实体有。但是，你应该有一个关系的属性 CustomerGroups 。只需设置你要进行相关的团体属性。例如，这将创建一个新的组名称为foo栏和相关的实体组。

Flying a little blind since you didn't include what properties entity has. But you should have a property for the relationship to CustomerGroups. Just set that property with the groups you want to be related to. For example, this would create a new Group name "foo bar" and relate the entity to that group.

using (var context = DataObjectFactory.CreateContext())
{
    entity.CustomerGroups = new List<CustomerGroup> { GroupName = "Foo bar" };
    context.Customers.Add(entity);
    context.SaveChanges();
    return entity.Id;
}

如果关系是正确设置，EF会自动记录插入 CustomerGroups 并插入一个关系到 CustomerInGroups 表。

If the relationship is setup correctly, EF will automatically insert a record into CustomerGroups and insert a relationship into the CustomerInGroups table.

编辑：

如果你想添加现有 CustomerGroup 来新的客户。你想获得 CustomerGroup 从数据库中第一，然后将其添加到您所插入的Customer实体。

If you're trying to add an existing CustomerGroup to a new Customer. You'll want to get the CustomerGroup from the database first, then add it to the Customer entity you're inserting.

using (var context = DataObjectFactory.CreateContext())
{
    var customerGroups = context.CustomerGroups.Where(...).ToList(); // get your CustomerGroup object(s) here, and ensure it's enumerated with ToList()
    entity.CustomerGroups = customerGroups;
    context.Customers.Add(entity);
    context.SaveChanges();
    return entity.Id;
}

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