Silverlight ListBox with ObservableCollection<T> and dynamic filter

Lets say I have this class:

public class MyData
{
    public bool IsActive{get;set;}
    public String Data1 {get;set;}
    public String Data2 {get;set;}
}

and an

ObservableCollection<MyData> data = new ObservableCollection<MyData>;
ListBox.ItemsSource = data;

Adding items to the ObservableCollectionworks as expected; however, I want to make sure that my开发者_Python百科 listbox only displays items where IsActive is set to 'true' -- I can't use a Linq query to set the ItemsSource because then its not an ObservableCollection, its IEnumerable and does not do any update notifications to the listbox.

Your answer is CollectionViewSource. Instead of binding to the list, bind to an instance of CollectionViewSource.

A slightly degenerate example follows (I am not sure if you're using ViewModels, Locators, etc to resolve your data and your list.)

Assume in your markup you have a CollectionViewSource declared in your resources as follows:

<phone:PhoneApplicationPage.Resources>
    <CollectionViewSource x:Key="src"/>
</phone:PhoneApplicationPage.Resources>

Then your list binding looks like:

<ListBox x:Name="MyListBox" ItemsSource="{Binding Source={StaticResource src}}">

Finally, in code you can marry your list and your collection view source:

        var collectionView = this.Resources["src"] as CollectionViewSource;
        // Check for null, etc.
        collectionView.Source = observableCollectionThatIAmBindingTo;
        collectionView.View.Filter=new Predicate<Object>(o => ((ItemType)o).IsActive );

Additionally, you may want to check out Bea Stollnitz' articles on the topic at:

http://bea.stollnitz.com/blog/?p=31

http://bea.stollnitz.com/blog/?p=392

The easier way is to use Visibility in XAML.

Supposed your ListBox ItemTemplate use StackPanel to hold your data, and in this case you have 2 TextBlock inside this StackPanel (1 for Data1, 1 for Data2).

So you should bind this StackPanel's Visibility with IsActive