XAML Binding to a CollectionViewSource property on a ViewModel

Question

I have a simple ViewModel like:

public class MainViewModel {
    ObservableCollection<Project> _projects;
    public MainViewModel() {
        // Fill _projects from DB here...
        ProjectList.Source = _projects;
        ProjectList.Filter = ...;
    }

    public CollectionViewSource ProjectList { get; set; }
}

I set the window's DataContext to a new instance of that ViewModel in the constructor:

public MainWindow() {
    this.DataContext = new MainViewModel();
}

Then in the Xaml I am attempting to bind the ItemsSource of a ListBox to that ProjectList property.

Binding just ItemsSource like so doesn't work:

<ListBox ItemsSource="{Binding ProjectList}" ItemTemplate="..." />

But if I first rebase the DataContext this works:

<ListBox DataContext="{Binding ProjectList}" ItemsSource="{Binding}" ItemTemplate="..." />

Shouldn't the first method work properly? What might I be doing wrong?

Are you getting your data from the DB synchronously or asynchronously ? — Timores, Jun 09 '10 at 20:03
synchronously, beside if it was a race condition then the second method would not work either... — joshperry, Jun 09 '10 at 20:11

score 19 · Accepted Answer · edited Jun 10 '10 at 16:56

19

If you are using CollectionViewSource you need to bind ItemsSource to ProjectList.View instead of ProjectList. That should solve your problem.

edited Jun 10 '10 at 16:56

joshperry

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answered Jun 09 '10 at 20:28

Joseph Sturtevant

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So I guess I can't duplicate my problem like that either... I've updated the question with what the ViewModel "really" looks like. – joshperry Jun 09 '10 at 23:10
See my updated answer. I'm not exactly sure why CollectionViewSource works this way, but its the way I've always had to work with them. – Joseph Sturtevant Jun 09 '10 at 23:59
4

Thank you, that's very helpful. This is the first time I've used a CollectionViewSource. I ended up making the property type `ICollectionView` and in the getter I return the `View` property from a private CollectionViewSource. That way I don't need to worry about binding to `.View` which would break if I change the collection type of that ViewModel property in the future. – joshperry Jun 10 '10 at 16:52

score 0 · Answer 2 · answered Jun 09 '10 at 20:32

0

From what you provided the first method should perfectly work. Devil lurks somewhere in details.

PS: Maybe you didn't specify implementation of INotifyPropertyChanged interface in sake of post size, but be careful in production. It's very easy to get a memory leak if you don't implement it.

answered Jun 09 '10 at 20:32

Anvaka

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Yes, it actually does implement that interface. Call it a test case if you will. – joshperry Jun 09 '10 at 23:12

XAML Binding to a CollectionViewSource property on a ViewModel

2 Answers2

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