Data Binding to Canvas.Left doesn't work

Question

I try to bind "Canvas.Left" to my data (<Setter Property="Canvas.Left" Value="{Binding X}" />) but it doesn't work. The getter for "X" and "Y" aren't called. The binding to "Content" works (<TextBlock Text="{Binding Content}" />). The getter for "Content" is called. Therefore I think "ItemsSource" is bound correctly. 

What's wrong with "Canvas.Left"?

      <ListBox DataContext="{Binding ViewModel}" ItemsSource="{Binding Elements}"
                      Margin="225,402,30,33" >
            
            <ListBox.ItemsPanel>
                <ItemsPanelTemplate>
                    <Canvas Background="LightGray"/>
                </ItemsPanelTemplate>
            </ListBox.ItemsPanel>

            <ListBox.ItemTemplate>
                <DataTemplate>
                    <TextBlock Text="{Binding Content}" />
                </DataTemplate>
            </ListBox.ItemTemplate>
            
            <ListBox.ItemContainerStyle>
                <Style TargetType="ListBoxItem">
                    <Setter Property="Canvas.Left" Value="{Binding X}" />
                    <Setter Property="Canvas.Top" Value="{Binding Y}" />
                </Style>
            </ListBox.ItemContainerStyle>

        </ListBox>

Thanks for helping,

Andreas Rossi

Answer 1

I have found that the way that you are suggesting doesn't work (not sure why, does work in WPF, if I recall correctly doesn't work in Silverlight either). My solution is to create a custom ListBox, like this:

public class CanvasListBox : ListBox
{
    protected override void PrepareContainerForItemOverride(DependencyObject element, object item)
    {
        FrameworkElement contentitem = element as FrameworkElement;
        Binding leftBinding = new Binding() { Path = new PropertyPath("X") };
        Binding topBinding = new Binding() { Path = new PropertyPath("Y") };
        contentitem.SetBinding(Canvas.LeftProperty, leftBinding);
        contentitem.SetBinding(Canvas.TopProperty, topBinding);

        base.PrepareContainerForItemOverride(element, item);
    }
}

This is just one of many situations in WinRT where you have to resort to code where data binding should work.  Hopefully this can be fixed before RTM.

...Stefan

Answer 2

Thank You for helping me.

Your code works well.

Andreas

Answer 3

I found this helpful, and it doesn't require code behind.

http://stackoverflow.com/questions/889825/is-it-possible-to-bind-a-canvass-children-property-in-xaml

Answer 4

I also noticed that embedding a Canvas within another Canvas works, but I don't know whether it's preferred.

<Canvas>
  <Canvas Canvas.Left="{Binding X}" Canvas.Top="{Binding Y}">
    ...
  </Canvas>
</Canvas>