RadExpander runtime error Telerik Ver. 2011.1.0315.1040

[Pawan Sharma]

We are getting run time silverlight error while loading Radexpander sometimes. We are using Silverlight 4 and telerik ver. 2011.1.0315.1040.
I have pasted the error below:

Message: Unhandled Error in Silverlight Application

Code: 4004   

Category: ManagedRuntimeError      

Message: System.InvalidOperationException: System.InvalidOperationException: Element is already the child of another element.

   at MS.Internal.XcpImports.MethodEx(IntPtr ptr, String name, CValue[] cvData)

   at MS.Internal.XcpImports.MethodEx(DependencyObject obj, String name)

   at System.Windows.Media.Animation.Storyboard.Begin()

   at Telerik.Windows.Controls.Animation.AnimationManager.Play(FrameworkElement target, String animationName, Action completeCallback, Boolean animateSelf, Object[] args)

   at Telerik.Windows.Controls.Animation.AnimationManager.Play(FrameworkElement target, String animationName, Boolean animateSelf)

   at Telerik.Windows.Controls.Animation.AnimationManager.Play(FrameworkElement target, String animationName)

   at Telerik.Windows.Controls.RadExpander.ChangeExpandedStates()

   at Telerik.Windows.Controls.RadExpander.OnApplyTemplate()

   at System.Windows.FrameworkElement.OnApplyTemplate(IntPtr nativeTarget)

   at MS.Internal.XcpImports.MethodEx(IntPtr ptr, String name, CValue[] cvData)

   at MS.Internal.XcpImports.MethodEx(DependencyObject obj, String name)

   at System.Windows.Media.Animation.Storyboard.Begin()

   at Telerik.Windows.Controls.Animation.AnimationManager.Play(FrameworkElement target, String animationName, Action completeCallback, Boolean animateSelf, Object[] args)

   at Telerik.Windows.Controls.Animation.AnimationManager.Play(FrameworkElement target, String animationName, Boolean animateSelf)

   at Telerik.Windows.Controls.Animation.AnimationManager.Play(FrameworkElement target, String animationName)

   at Telerik.Windows.Controls.RadExpander.ChangeExpandedStates()

   at Telerik.Windows.Controls.RadExpander.OnApplyTemplate()

   at System.Windows.FrameworkElement.OnApplyTemplate(IntPtr nativeTarget)    

Please let us know what is causing this to occur and workaround for this issue.

Thanks

[Tina Stancheva]

Hi Pawan Sharma,

We are not aware of this issue. And I wasn't able to reproduce it locally. Can you please give us more details about the scenario in which the RadExpander is used. Also, have you updated the version of the controls?

During the Q1 2011 the RadExpander control went under extensive changes. Our goal was to improve the performance of the control and fix many of the bugs. However, we couldn't achieve this without introducing some changes in its default ControlTemplate. And if you have applied a custom style for the control, this might be causing exceptions but unfortunately I cannot be sure without having more information about your  implementation of the control.

All the best,
Tina Stancheva
the Telerik team