Raccoltaview.Deferrefresh () getta eccezione

Question

Ci sono casi in cui si hanno molti aggiornamenti UI dovuti a una massiccia quantità di eventi inotifyfychangedproperties.In tal caso potresti voler segnalare le modifiche all'UI solo una volta quando tutte le proprietà sono impostate in un lotto.

Ho trovato questo ottimo articolo che spiega come rinviare l'aggiornamento del mirino:

http://marlonggrech.wordpress.com/2008/11/11/22 / ICollectionView-Spiegato /

Comunque ottengo un'eccezione quando la vista è differita e cerco di aggiungere qualcosa alla raccolta.Non capisco perché questo non dovrebbe essere permesso.Questo è l'intero punto di questo al primo posto.

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InvalidOperationException: Non può cambiare o controllare il contenuto o la posizione corrente di CollectionView mentre si aggiorna viene differita.

Qualcuno sa come risolvere questo problema? Molte grazie,

Answer 1

Yes, don't modify the collection in question. I think that you are misunderstanding the purpose of a collection view. This is what MSDN says;

You can think of a collection view as a layer on top of a binding source collection that allows you to navigate and display the collection based on sort, filter, and group queries, all without having to manipulate the underlying source collection itself.

So in short, don't defer the refresh until you are done adding and removing, and otherwise manipulating your collection.

Answer 2

I think you are misunderstanding or misrepresenting the MSDN help on the subject. They are saying that you don't have to modify the underlying collection to sort or filter. They are not saying that you can't modify the underlying collection. The OP has a very valid point. We have a large collection that has been sorted and filter for the user and it is displayed in a list box. When the user selects a range of those records and wants to delete them, we are forced into a situation where the ListCollectionView refreshs view for every item that was deleted.

I think the OP's question is very valid. The performance is horrendous because we have multiple filters on a huge set of data. The DeferRefresh has a real purpose on a class like the ListCollectionView, but in inexplicably diabled for inserts and deletes, when you need it the most.