Drag and Drop is not fired

[lee doo]

Hi guys
I have a problem with DragDropManager
Our project is consisted of  several silverlight applacations.
Telerik application is main frame of our projects.
We tried to use RadDragAndDropManager to chart components.
But, OnDragQuery is not fired. 
Do variable of the OnDragQuery have requirement?
We can drag a grid data, but not chart data.
Actually, the chart data is DevExpress.Xpf.Charts.

here is our code of the chart for XAML

<dxc:ChartControl x:Name="radChart" EnableAnimation="True" BorderThickness="0"  telerik:RadDragAndDropManager.AllowDrag="True"
                              telerik:RadDragAndDropManager.AllowDrop="True">

  next is OnDragQuery code for C#

private void AddDragDropHandlers(DependencyObject chart)
{
RadDragAndDropManager.AddDragQueryHandler(chart, OnDragQuery);
RadDragAndDropManager.AddDragInfoHandler(chart, OnDragInfo);
RadDragAndDropManager.AddDropQueryHandler(chart, OnDropQuery);
RadDragAndDropManager.AddDropInfoHandler(chart, OnDropInfo);
}

I folllowed my data flow.
The chart data entered to The AddDragQueryHandler, but the event was not fired.

Could you help me?

Thanks