thanks Mick, but it messed up my layout a bit. I did something simpler.
I use the Silverlight Toolkit for WP7 and add a GetureListener pinch to my grid
<toolkit:GestureService.GestureListener> <toolkit:GestureListener PinchDelta="GestureListener_PinchDelta" /> </toolkit:GestureService.GestureListener>
and code in the event
private void GestureListener_PinchDelta(object sender, PinchGestureEventArgs e) { if (e.DistanceRatio < 1.0 || e.DistanceRatio > 1.4) { return; } // Create the animation for pinch Storyboard storyboard = new Storyboard(); DoubleAnimation pinchXAnimation = new DoubleAnimation(); pinchXAnimation.To = e.DistanceRatio; pinchXAnimation.Duration = TimeSpan.FromSeconds(0.3); storyboard.Children.Add(pinchXAnimation); Storyboard.SetTargetProperty(pinchXAnimation, new PropertyPath("GridScaling.ScaleX")); Storyboard.SetTarget(pinchXAnimation, GridScaling); DoubleAnimation pinchYAnimation = new DoubleAnimation(); pinchYAnimation.To = e.DistanceRatio; pinchYAnimation.Duration = TimeSpan.FromSeconds(0.3); storyboard.Children.Add(pinchYAnimation); Storyboard.SetTargetProperty(pinchYAnimation, new PropertyPath("GridScaling.ScaleY")); Storyboard.SetTarget(pinchYAnimation, GridScaling); storyboard.Begin(); }