WPF绑定到自定义属性不起作用

Question

I have this control to display a list of usercontrols

<ItemsControl x:Name="LayersList" Margin="10,284,124,0">
    <ItemsControl.ItemsPanel>
        <ItemsPanelTemplate>
            <StackPanel Orientation="Vertical"/>
        </ItemsPanelTemplate>
    </ItemsControl.ItemsPanel>
    <ItemsControl.ItemTemplate>
        <DataTemplate>
            <NaturalGroundingPlayer:LayerControl Item="{Binding}"/>
        </DataTemplate>
    </ItemsControl.ItemTemplate>
</ItemsControl>

The LayerControl control contains this code

public partial class LayerControl : UserControl {
    public LayerItem Item { get; set; }

    public static readonly DependencyProperty ItemProperty =
    DependencyProperty.Register(
        "Item",
        typeof(LayerItem),
        typeof(LayerControl),
        new PropertyMetadata(null));

    public LayerControl() {
        InitializeComponent();
    }

    private void Button_Click(object sender, RoutedEventArgs e) {
        // This doesn't work because Item remains null
        MainWindow.Instance.LayersList.Items.Remove(Item);
    }
}

LayerItem contains this

[PropertyChanged.ImplementPropertyChanged]
public class LayerItem {
    public LayerType Type { get; set; }
    public string FileName { get; set; }
}

public enum LayerType {
    Audio,
    Video,
    Image
}

Problem is: The Binding is setting the Item property to null. If I change the binding to {Binding Type} instead of {Binding} (and adapt the property type accordingly), then it works. But I can't find a way to bind the whole object. What am I doing wrong?

On a side note, I tried setting ItemsControl.ItemsSource to a ObservableCollection<LayerItem> but that didn't seem to work. Adding items directly to ItemsControl.Items is working. Any idea why that is?

Answer 1

You have incorrectly implemented a dependency property. You should use GetValue and SetValue methods instead of creating an auto-property.

public static readonly DependencyProperty ItemProperty = 
    DependencyProperty.Register(
        "Item", typeof(LayerItem), typeof(LayerControl));

public LayerItem Item
{
    get { return (LayerItem)GetValue(ItemProperty); }
    set { SetValue(ItemProperty, value); }
}

PS You shouldn't access controls like this: MainWindow.Instance.LayersList.Items.Remove(Item) . You should use MVVM instead. I'm also not convinced this property is required at all. DataContext may be enough.