LINQ to SQL的错误ForeignKeyReferenceAlreadyHasValueException [英] LINQ to SQL ForeignKeyReferenceAlreadyHasValueException error

问题描述

当我试图改变一个外键正在生成此错误。
我知道这是一个非常常见的错误，我发现吨关于它的信息，并试图实现我找到了修复，但尝试更新密钥时，我仍然得到这个错误。 参考螺纹

This error is being generated when I try to change a foreign key. I know this is a very common error I’ve found tons of information about it and tried to implement the fixes I’ve found but I still get this error when trying to update Keys. Reference Thread

本来我只是直接分配值，而不是试图将实体映射。

Originally I was just directly assigning the value and not trying to map the entities.

ticket.assigned_to_group = assigned_to

我从此改变了尝试，并映射实体，我认为正确的答案;但我仍然得到错误。

I’ve since changed to try and map the entities which I believe the correct answer; however I still get the error.

ticket.assigned_to_group = db.sub_units.Single(f => f.id == assigned_to).id;

知道为什么这是行不通的。另外，如果我有多个外键的表，我真的需要为每个键做一个新的查询，或是否有更好的办法？

Any idea why this would not work. Also if I have a table with multiple foreign keys, do I really need to do a new query for each key or is there a better way?

推荐答案

我想你想指定一个ID，当你需要分配的实体。 （我不是100％肯定这是你在做什么）

I think you are trying to assign an ID when you need to assign the entity. (I'm not 100% sure this is what you are doing)

// Don't assign just the id
Person.ParentId = parentId;

// Assign the entity
Person.Parent = db.Parents.Single(x.Id == parentId);

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