Fire event when ItemsSource of ListView changes

Question

I can't find an event that can be called after a window was loaded, and where i can get access to the ItemsSource of a ListView. The only thing i can think is the Loaded event in the ListView but when this event is fired the ItemsSource remains null.

I probably need another event so i can know what is in the ItemsSource.

So with code i will probably expose better what i am trying to do:

In a custom class:

public class GridViewSomething
{
    public static readonly DependencyProperty TestProperty =
        DependencyProperty.RegisterAttached("Test",
        typeof(bool),
        typeof(GridViewSomething),
        new UIPropertyMetadata(OnTestChanged));

    public static bool GetTest(DependencyObject obj)
    {
        return (bool)obj.GetValue(TestProperty);
    }

    public static void SetTest(DependencyObject obj, bool value)
    {
        obj.SetValue(TestProperty, value);
    }

    static void OnTestChanged(object sender, DependencyPropertyChangedEventArgs e)
    {
        ListView listView = sender as ListView;

        if (!(bool)e.OldValue && (bool)e.NewValue)
            listView.AddHandler(ListView.LoadedEvent, new RoutedEventHandler(ListView_Loaded));
        else if (!(bool)e.NewValue && (bool)e.OldValue)
            listView.RemoveHandler(ListView.LoadedEvent, new RoutedEventHandler(ListView_Loaded);
    }

    static void ListView_Loaded(object sender, RoutedEventArgs e)
    {
        ListView listView = sender as ListView;

        if (listView.ItemsSource != null)
        {
            //Do some work
        }
    }
}

And the ListView:

(...)

<ListView ItemsSource="{Binding Students}"
          test:GridViewSomething.Test="True">

(...)

I am binding the ListView to a Collection in the ViewModel of this Window. I need to know precisely what is in the ItemsSource in that custom class.

So how i can achieve this?

Thanks in advance!

You already know that the bound colection is the ItemsSource, why would you need it to be in the view to do something? — H.B., Nov 27 '11 at 22:23
What i am trying to do is auto generate the columns based on the bound collection to the ListView... It's why i am tring to do this way. I don't have many experience with DependencyProperties and this a first idea, and it's why i am trying to find the appropriated event to be called that look into an array of strings in the collection (through the ItemsSource) and add a GridView with the Columns to the ListView. — Miguel, Nov 27 '11 at 22:30
Try out overriding OnApplyTemplate, but why you need that perhaps solution in an other place? — sll, Nov 27 '11 at 22:41

score 2 · Accepted Answer · edited May 23 '17 at 12:32

2

You could subsribe to changes on the ItemsSource property by using a descriptor as shown here. If check the value in that handler it should not be null (unless the bound property was in fact set to null).

edited May 23 '17 at 12:32

Community

1
1

answered Nov 27 '11 at 22:51

H.B.

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You mean the DependencyPropertyDescriptor? I am a bit confused now, how it works and where it should be applied? – Miguel Nov 27 '11 at 23:21
@Miguel: You can subscribe in the constructor of your window for example, or in the loaded event of the ListView. – H.B. Nov 27 '11 at 23:38
It worked. Thanks! I started really recently working with DependencyProperties so i don't have any experience using them or know what we have to do the stuff we need but they are really useful and helpful. – Miguel Nov 28 '11 at 00:59

Fire event when ItemsSource of ListView changes

1 Answers1