CODEWITHSUNDEEP
c#wpfentity-frameworkmvvm
deafie
deafie

Reputation: 13

Moving to a specific item in CollectionViewSource?

I'm new at WPF and I'm trying to use MVVM. I'm using CollectionViewSource in my view-model against a SQL database using Entity Framework.

So let's say I have this class:

public class People
{   
    public int Id { get; set; }
    public string name { get; set; }
}

And lets say this is what I have in the database:

ID: Name:

  1. Bugs Bunny

  2. Mick Jagger

  3. Mickey Mouse

  4. Donald Duck

  5. Goofy

  6. Elmer Fudd

  7. Daffy Duck

  8. Porky Pig

Now using CollectionViewSource.View, I know how to use the methods MoveCurrentToNext(), MoveCurrentToPrevious(), etc. and that works fine, but I need to move to a specific name, for example Donald Duck. So if I do this:

dbContext.Peoples.Find(4);

Or if I do this

dbContext.Peoples.Where(p => p.Name == "Donald Duck").FirstOrDefault();

That will get me the right object from the database using Entity Framework. However, if I do this:

CollectionViewSource.View.MoveCurrentTo(dbContext.Peoples.Find(4));

It will not move, and CollectionViewSource.View.CurrentItem is null.

So then how would someone move to the correct item?

Upvotes: 1

Views: 1371

Answers (1)

Bruno
Bruno

Reputation: 1974

I guess this is because the reference that you get when calling dbContext.Peoples.Find(4) is not the same as the one you have in your CollectionView source collection.

The CollectionViewSource.View.MoveCurrentTo (an others 'MoveTo' methods of the collectionView) requires an argument that is the same reference as the one in your source collection.

Then, if your dbContext methods to retreive an object returns a new instance or an instance different than the one in your CollectionView, this won't work.

So either use an intermediate collection as the source of the collection view to keep a unique reference to the objects (and update these references when the object in in data access context change) or try to implement equality members in your People class (never tried the later solution but should work).

Also, try to add in your question some complete piece of code rather than code fragments about which we can't realy see exactly where is the problem.

Upvotes: 2

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