绑定到ListBox ItemContainerStyle中的ListBoxItem属性

Question

Hello stackoverflowers,

I would like to set property canvas.left on the ListBoxItems of my ListBox. I'm trying this :

 <ListBox.ItemContainerStyle>
                    <Style TargetType="ListBoxItem">
                        <Setter Property="Canvas.Left" Value="{Binding Content.StartPoint.X, Mode=TwoWay, RelativeSource={RelativeSource Self}}"/>
                        <Setter Property="Canvas.Top" Value="{Binding Content.StartPoint.Y}"/>
                        <Setter Property="Template">
                            <Setter.Value>
                                <ControlTemplate TargetType="ListBoxItem">
                                    <ContentPresenter/>
                                </ControlTemplate>
                            </Setter.Value>
                        </Setter>
                    </Style>
</ListBox.ItemContainerStyle>

But it says it can't resolve content property in my datacontext.

I tried

<Setter Property="Canvas.Left" Value="{Binding Content.StartPoint.X}, Mode=TwoWay, RelativeSource={RelativeSource Self}}/>

But then it can't resolve StartPoint in datacontext object.

So i wonder how can i bind to the properties of my listbox items ??

EDIT : I'm binding ListBox ItemsSource to an ObservableCollection. The view is a UserControl.

EDIT 2 :

My listbox is binded to an observable collection of objects derivated from Foo.

Foo object defines StartPoint.

 public abstract class Foo: INotifyPropertyChanged
    {
      protected Point m_startPoint;

      public double Height { get; set; }

      public double Width { get; set; }

      public Point StartPoint
      {
         get { return m_startPoint; }
         set
         {
            m_startPoint = value;

            Width = Math.Abs(m_startPoint.X - m_endPoint.X);
            Height = Math.Abs(m_startPoint.Y - m_endPoint.Y);

            OnPropertyChanged(nameof(StartPoint));
            OnPropertyChanged(nameof(Width));
            OnPropertyChanged(nameof(Height));
        }
     }

Answer 1

Provided that your ListBox is actually bound to a collection of Foo (or derived) objects, the bindings should look like this:

<Setter Property="Canvas.Left" Value="{Binding StartPoint.X}"/>
<Setter Property="Canvas.Top" Value="{Binding StartPoint.Y}"/>

The reason is that the DataContext of each ListBoxItem is set to the corresponding data item from the ItemsSource collection, ie the corresponding Foo instance.