Exception animating a scale layout transform in WPF

Question

I have create a storyboard in C# to animation a scale transform on a canvas. The scale transform is a layout transform. Here is my C# code for the animation:

Storyboard Configuring = new Storyboard();
if (NexusRoot != null)
{
var current = (NexusRoot.LayoutTransform as ScaleTransform).ScaleX;

Duration duration = new Duration(TimeSpan.FromSeconds(1));

DoubleAnimation myDoubleAnimation1 = new DoubleAnimation();
myDoubleAnimation1.Duration = duration;
Configuring.Children.Add(myDoubleAnimation1);
myDoubleAnimation1.From = current;
myDoubleAnimation1.To = scale;
Storyboard.SetTarget(myDoubleAnimation1, NexusRoot);
Storyboard.SetTargetProperty(myDoubleAnimation1, (PropertyPath)new PropertyPathConverter().ConvertFromString("(UIElement.LayoutTransform).(ScaleTransform.ScaleX)"));

DoubleAnimation myDoubleAnimation2 = new DoubleAnimation();
myDoubleAnimation2.Duration = duration;
Configuring.Children.Add(myDoubleAnimation2);
myDoubleAnimation2.From = current;
myDoubleAnimation2.To = scale;

Storyboard.SetTargetName(myDoubleAnimation2, "NexusRoot");
Storyboard.SetTargetProperty(myDoubleAnimation2, (PropertyPath)new PropertyPathConverter().ConvertFromString("(UIElement.LayoutTransform).(ScaleTransform.ScaleY)"));
}

When i run this animation it throws the following exception.

System.ArgumentNullException was caught Message="Value cannot be null.\r\nParameter name: dp"
Source="WindowsBase" ParamName="dp" StackTrace: at System.Windows.DependencyObject.GetValue(DependencyProperty dp) at System.Windows.Media.Animation.Storyboard.ProcessComplexPath(HybridDictionary clockMappings, DependencyObject targetObject, PropertyPath path, AnimationClock animationClock, HandoffBehavior handoffBehavior, Int64 layer) at System.Windows.Media.Animation.Storyboard.ClockTreeWalkRecursive(Clock currentClock, DependencyObject containingObject, INameScope nameScope, DependencyObject parentObject, String parentObjectName, PropertyPath parentPropertyPath, HandoffBehavior handoffBehavior, HybridDictionary clockMappings, Int64 layer) at System.Windows.Media.Animation.Storyboard.ClockTreeWalkRecursive(Clock currentClock, DependencyObject containingObject, INameScope nameScope, DependencyObject parentObject, String parentObjectName, PropertyPath parentPropertyPath, HandoffBehavior handoffBehavior, HybridDictionary clockMappings, Int64 layer) at System.Windows.Media.Animation.Storyboard.BeginCommon(DependencyObject containingObject, INameScope nameScope, HandoffBehavior handoffBehavior, Boolean isControllable, Int64 layer) at System.Windows.Media.Animation.Storyboard.Begin() at StormFront.NexusDesigner.ScaleCanvasAnimation(Double scale) in C:\Documents and Settings\lbeaver\Desktop\StormFront\WPF\StormFront\StormFront\NexusDesigner.xaml.cs:line 544 InnerException:

How do i stop this exception from happening?

Answer 1

I found my problem. The problem is in the property path. I was using UIElement and should have been using FrameworkElement.

So this line:

Storyboard.SetTargetProperty(myDoubleAnimation1, (PropertyPath)new PropertyPathConverter().ConvertFromString("(UIElement.LayoutTransform).(ScaleTransform.ScaleX)"));

should be:

Storyboard.SetTargetProperty(myDoubleAnimation1, (PropertyPath)new PropertyPathConverter().ConvertFromString("(FrameworkElement.LayoutTransform).(ScaleTransform.ScaleX)"));