Entity Framework 4.1 DbSet Reload
c#, entity-framework-4.1
Solution
This is not the way you are supposed to use `DbContext`, and because of that it is almost impossible to reload the data. Keeping a single context around for a long time is incorrect usage. The link will also answer why your tracked entities are not updated.
You can selectively reload a single entity by calling `Reload` on `DbEntityEntry`:
context.Entry(entity).Reload();
You can also revert back to `ObjectContext` and use `ObjectQuery` with `MergeOption.OverrideChanges`, or use `Refresh` for a collection of entities with `RefreshMode.StoreWins`.
All these approaches suffers some problems:
- If the record is deleted in the database, it will not be removed from the context.
- Changes in relations are not always refreshed.
The only correct way to get fresh data is `Dispose` the context, create a new one and load everything from scratch - and you are doing this anyway.
Problem
I'm using a single instance of `DbContext` scenario to shadow entire copy of the database locally in a WPF app. I've heard this is bad practice, but my database is small and I need an entire copy of it locally while the app is running. An extension method for `IQueryable`, `Load()` lets me preload the elements of a `DbSet<>`, so that I can bind things to the Local property of `DbSet<>`. Data in the database changes rapidly, so I want to `SaveChanges()` and reload everything, even objects that are already tracked. Calling the `Load()` method again doesn't update the items that are tracked but are not marked as changed, which are already loaded. What is the preferred method of reloading the preloaded items in a `DbSet<>`? Off the top of my head, I can only think of calling `SaveChanges()`, then go through all entries and set both tracked and original values to the current values in the database, then `Load()` whatever new objects that might have been added. In my scenario it's not possible to delete objects, but I might have to support item deletion in the long run. This doesn't seem right, there should be a way to drop everything and reload. It would seem that it's easier to drop my context and just start anew, but all the elements in WPF are already bound to the `Local´ObservableCollection<>`, and this just messes up the interface.