title: Entity Framework - how to come with failure when saving data
body: <p>let's suppose the situation looks like this: I have one object context in my app and I download 15k records from the db (like 15k invoices). User picks one and makes some changes to it. I call SaveChanges() and it fails for some reason (doesn't matter what reason).</p>
  
  <p>Now the context that was used can't perform any save because it wasn't able to save those changes. What should I do to make it work?</p>
  
  <p>Another scenario is that I use a separate context for making changes. If saving fails then nothing happens - I discard the context and that's it. The problem that arises is: how to merge changes back to the main context? (without downloading 15k records once again)</p>