它为空，因为您尚未请求Entity Framework检索关联。

It's null because you haven't asked Entity Framework to retrieve the association.

有两种方法：

1 - 延迟加载 / p>

1 - Lazy Loading

var reciever = db.Recievers.SingleOrDefault();
var receiverPackets = receiver.Packets; // lazy call to DB - will now be initialized

我不喜欢这种方法，我个人关闭延迟加载，并使用其他方法

I don't like this approach, i personally turn off lazy loading, and use the other approach

2 - Eager Loading b

var receiver = db.Receivers.Include("Packets").SingleOrDefault();

这导致接收器和数据包之间的LEFT OUTER JOIN，而不是两个调用懒惰加载。

Which results in a LEFT OUTER JOIN between Receivers and Packets, instead of two calls - which is the case with lazy loading.

这是否能解答你的问题？

Does that answer your question?