使用LINQ和实体如何返回多对多关系的值

问题描述

我有两个实体，帐户和订阅与它们之间的多对多关联。我似乎无法在教程中找到任何地方如何执行以下操作：

我想查找具有类型x的订阅的所有帐户。如果我没有使用Entity框架，我可以加入AccountSubscription表，但是不能通过Entity访问。如果我需要查询多对多的关系，我必须创建一个特殊的实体吗？

解决方案

EF应该创建一种多对多关系的导航属性。那么你应该可以这样做：

  var accounts = from a in Accounts 
 where a.Subscriptions .Any（s => s.SubscriptionType ==something）
选择一个; 
  

例如，我有一个简单的数据库，产品和组之间有很多关系：

而EF创建关联在模型中：

所以我可以创建一个这样的查询（这里包括组，所以我可以看到类别）：

I have two entities, Account and Subscription with a many-to-many association between them. I can't seem to find in the tutorials anywhere how to do the following:

I want to find all the Accounts with a Subscription of type x. If I wasn't using the Entity framework I could join to the AccountSubscription table, but that isn't accessible via Entity. Do I have to create a special entity if I need to query on a many-to-many relationship?

解决方案

EF should create a navigation property for a many-to-many relationship. Then you should be able to do something like this:

var accounts = from a in Accounts
               where a.Subscriptions.Any(s => s.SubscriptionType == "something")
               select a;

For example, I have a simple db with a many to many relationship between Products and Groups:

And EF creates the association in the model:

So I can create a query like this (here including the Groups so I can see the Category):

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