How to postpone an update to a Binding in WPF

Question

Is there an easy way to tell a Two-way WPF data binding to wait a few milliseconds after the last change before updating the Source with the new property value?

I'm implementing a filter feature for a ListBox where I have a textbox, and I want to filter the content of the ListBox according to what I type. I'm using data binding to connect the pieces together. Filtering the list can be quite time consuming, so I don't want to do it after every character that is typed: hence my request.

I have been using Paul Stovell's DelayBinding Extension (his site's down at the moment, so I can't link to it). However, I suspect that it is the cause of a memory leak in my applicataion (caused by it not removing event handlers).

Does anybody else have any other ideas?

Answer 1

First, to answer your question, I would add the UpdateSourceTrigger binding extension which will let you control when the binding updates. Try LostFocus first but it sounds like you might want to go for Explicit.

Second, if your filtering takes a long time I would look into using CollectionViewSource on your ListBox. Bea Stollnitz has a good primer on it here and I used this blog post to show me how to filter. When I changed over I noticed a huge speed difference over my other implementation even though they use the same filtering functions. Also CollectionViewSource will automatically handle updating filtered items if the list you're bound to changes, even on the item level if you're binding to an ObservableCollection (this is the original reason I changed to CollectionViewSource).

HTH