插入引用现有记录的新行的 Linq 问题

作者: 夢De预見
来源: 51数据库
2022-12-13

问题描述

(我相信这与这个，但那里没有答案，我想我可以在这里更好地表达问题......)

(I believe this is the same problem as this one, but there's no answer there, and I think I can express the problem better here...)

我有两个 Linq-to-SQL 类，State 和 County，其中 County 有一个 FK 到 State.这是一些测试代码:

I have two Linq-to-SQL classes, State and County, where County has a FK to State. Here's some test code:

State s = State.GetState("NY"); // here I do a load of a State class via the Linq DataContext
County c = new County();
c.Name = "Rockland";
c.State = s;
MyDataContext.GetTable<County>().InsertOnSubmit(c);
MyDataContext.SubmitChanges(); // throws an exception

抛出的异常是违反PRIMARY KEY约束'PK_State'.不能在对象'dbo.State'中插入重复键".

换句话说，这里似乎发生的事情是，尽管我已将 s 作为现有记录加载，但当我尝试插入 c 时，Linq 假设所有相关的对象，包括State，也需要插入！

In other words, what appears to be happening here is that despite my having loaded s as an existing record, when I attempt to insert c, Linq is assuming that all related objects, State included, also need to be inserted!

这完全是荒谬的，我无法相信微软会犯这么大的错误——所以一定是我自己的理解有问题.

This is completely absurd, and I cannot believe that Microsoft would have made such a huge blunder - so it must be that somewhere my own understanding is faulty.

谁能解释一下我做错了什么，这里的正确方法是什么?

Can anyone please explain what I am doing wrong, and what the correct approach here is?

谢谢！