CollectionView.deferrefresh () lança exceção

Question

Há casos quando você tem muitas atualizações da interface do usuário devido a uma quantidade massiva de eventos inotifychangedproperties.Nesse caso, você pode desejar sinalizar as alterações na interface do usuário apenas quando todas as propriedades estiverem definidas como em um lote.

Eu achei este grande artigo que explica como adiar a atualização do viewCollection:

http://marlongrech.wordpress.com/2008/11/22 / ICollectionView-explicou /

No entanto, recebo uma exceção quando a vista é adiada e tento adicionar algo à coleção.Eu não entendo porque isso não deve ser permitido.Esse é o ponto inteiro dele em primeiro lugar.

.

InvalidOperationException: Não pode alterar ou verificar o conteúdo ou a posição atual de CollectionView enquanto a atualização está sendo diferida. Alguém sabe como resolver esse problema? Muito obrigado,

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.