c# - why can't we get ObjectContext from an EntityObject

Question

It is well know that if we have an EntityObject that there is no way to find the ObjectContext that it belongs to. That's fair enough I guess, but why is it that we can lazy load objects then? Surely the process of lazy loading has to get access to the ObjectContext in order to load the new objects?

Answer 1

You are right, given an object, we don't know what context it belongs to, or what session it is attached to. But Lazy Loading happens like this :

var firstPost = _Context.Posts.First()
var commentList = firstPost.Comments

When you say _Context.Posts.First() then one post is loaded. Then when you say firstPost.Comments that's when the comments list is loaded.

This is possible because the type of your Comments field in your Post is probably an IList or some such generic interface : this is because EF4 can put a proxy list instead of the actual comment list. The proxy list knows about the _Context - knows about which session or context it is attached to. Hence it is able to load an actual list on demand.