Document 'Disconnected Entities' - The code example in the Handling Deletes section works unexpected

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Hi,

In the section 'Handling Deletes' there is a code example for handling true deletes using a graph diff. However I noticed that (at least for me) it worked unexpected when u are using integer PK's. For example when you send an aggregate like blog with 3 new posts. the posts are new and so the Id = 0. The first post gets added like expected but the next ones are not because now there is already one with id=0 so those posts are not added.

This behavior is caused by the following lines:
`var existingPost = existingBlog.Posts
.FirstOrDefault(p => p.PostId == post.PostId);

if (existingPost == null)
{
existingBlog.Posts.Add(post);
}
else
{
context.Entry(existingPost).CurrentValues.SetValues(post);
}`

For me it works expected when I change it to:
`var existingPost = existingBlog.Posts
.FirstOrDefault(p => p.PostId == post.PostId && p.PostId != 0)`

Perhaps this should be mentioned in the docs or the example updated?