Moving a Control on a Canvas on Drag & Drop

Question

I have placed text blocks on a canvas. I change their position on mouse drag using the following code:

   protected bool isDragging;
   private Point clickPosition;

   private void txt_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
    {
            isDragging = true;
            var draggableControl = sender as TextBlock;
            clickPosition = e.GetPosition(this);
            draggableControl.CaptureMouse();
    }

    private void txt_MouseLeftButtonUp(object sender, MouseButtonEventArgs e)
    {
        isDragging = false;
        var draggable = sender as TextBlock;
        draggable.ReleaseMouseCapture();
    }

    private void txt_MouseMove(object sender, MouseEventArgs e)
    {
        var draggableControl = sender as TextBlock;

        if (isDragging && draggableControl != null)
        {
            Point currentPosition = e.GetPosition(this.Parent as UIElement);

            var transform = draggableControl.RenderTransform as TranslateTransform;
            if (transform == null)
            {
                transform = new TranslateTransform();
                draggableControl.RenderTransform = transform;
            }

            transform.X = currentPosition.X - clickPosition.X;
            transform.Y = currentPosition.Y - clickPosition.Y;
        }
    }

What I want here is to get the new position of the textblock, save it and next time when the application loads, the control should take the new position. I understand that my code does not change the Left & Top property of the textblock, but instead transforms it. Hence, the Left and Top Property won't be changed. I tried to set Left and Top Property as

            draggableControl.SetValue(Canvas.LeftProperty, transform.X);
            draggableControl.SetValue(Canvas.TopProperty, transform.Y);

But it also does not change it.

What can be done to achieve the desired?

Answer 1

You must not use Transform...but only

draggableControl.SetValue(Canvas.LeftProperty, X);
draggableControl.SetValue(Canvas.TopProperty, Y);

because transform affect only rendering