custom adorners get parent

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WPF

Hello codeproject!

In my project in WPF, I have implemented a drag drop functionality.
Where items can be dropped on a canvas. I can add a custom adorner nodes of type control to the SELECTED ITEM on the canvas at RUNTIME. However, when i tried to walk down
to the nodes' parent tree at previewmouseleftbuttondown. I can no longer retrieve the canvas parent. It takes shorcut to a type grid,below is the xaml.

Grid>
ScrollViewer Name="CanvasScrollViewer"
    Background="Transparent"
    HorizontalScrollBarVisibility="Auto"
    VerticalScrollBarVisibility="Auto">

n:MyCanvas x:Name="TheCanvas"
     MinHeight="800"
     MinWidth="1000"
     AllowDrop="True"
     Background="White">
/n:MyCanvas>
/ScrollViewer>
/Grid>

Thanks in advanced! :)