I want to wrap some Rectangles on a Canvas.The details of rectangles are in a list in my viewmodel.I succeeded drawing the rectangles,but failed to make them movable.In my eventhandler Canvas.GetLeft() and Canvas.SetLeft dosen’t work.

here is my ItemsControl:

<ItemsControl Width="1920"
                Height="1080"
                ItemsSource="{Binding Controls,Mode=TwoWay}">
    <ItemsControl.ItemsPanel>
        <ItemsPanelTemplate>
            <Canvas />
        </ItemsPanelTemplate>
    </ItemsControl.ItemsPanel>
    <ItemsControl.ItemTemplate>
        <DataTemplate>
            <UniformGrid Rows="2"
                            PreviewMouseUp="Container_Control_MouseUp"
                            PreviewMouseMove="Container_Control_MouseMove"
                            PreviewMouseDown="Container_Control_MouseDown">
                <Rectangle Width="{Binding Width}"
                            Height="{Binding Height}"
                            Fill="Blue" />
                <TextBlock Grid.Row="1"
                            Text="move it" />
            </UniformGrid>
        </DataTemplate>
    </ItemsControl.ItemTemplate>
    <ItemsControl.ItemContainerStyle>
        <Style>
            <Setter Property="Canvas.Top"
                    Value="{Binding X}" />
            <Setter Property="Canvas.Left"
                    Value="{Binding Y}" />
        </Style>
    </ItemsControl.ItemContainerStyle>
</ItemsControl>        

and here is my eventhandlers,they don’t work with elements in a itemscontrol:

public partial class ControlsView : UserControl
    {
        bool _isMouseDown = false;
        Point _mouseDownPosition;
        Point _mouseDownControlPosition;
        public ControlsView(ControlsViewModel vm)
        {
            this.DataContext = vm;
            InitializeComponent();
        }
        private void Container_Control_MouseUp(object sender, MouseButtonEventArgs e)
        {
            var c = sender as UIElement;
            _isMouseDown = false;
            c.ReleaseMouseCapture();
        }
        private void Container_Control_MouseMove(object sender, MouseEventArgs e)
        {
            if (_isMouseDown)
            {
                var c = sender as UIElement;
                var pos = e.GetPosition(this);
                var dp = pos - _mouseDownPosition;
                Canvas.SetLeft(c, _mouseDownControlPosition.X + dp.X);
                Canvas.SetTop(c, _mouseDownControlPosition.Y + dp.Y);
            }
        }

        private void Container_Control_MouseDown(object sender, MouseButtonEventArgs e)
        {
            var c = sender as UIElement;
            _isMouseDown = true;
            _mouseDownPosition = e.GetPosition(this);
            _mouseDownControlPosition = new Point(double.IsNaN(Canvas.GetLeft(c)) ? 0 : Canvas.GetLeft(c), double.IsNaN(Canvas.GetTop(c)) ? 0 : Canvas.GetTop(c));
            c.CaptureMouse();
        }
    }