Cannot access drag adorner template - wpf

Question

I've used the sample code provided by Bea Stollnitz (http://bea.stollnitz.com/blog/?p=53), in order to enable drag and drop in my application, and drag adorner, etc.
Everything works fine, my drag adorner is well displayed, I have all the behavior I want.
But (yes there is always a but), I cannot access the DataTemplate of the Drag Adorner, in order to display different data depending on the dragged data.
I have simplified the code, but the basics are still there.
This is the DataTemplate of my DragAdorner
<DataTemplate x:Key="DragAndDropTemplate" DataType="{x:Type MyType}">
<Grid>
<Grid Opacity="0.5">
<Border x:Name="HeaderBorder" CornerRadius="2" BorderThickness="1" Margin="5,2,5,2">
<Border x:Name="InsideBorder" CornerRadius="2" BorderThickness="1">
<TextBlock x:Name="number" Text="{Binding Name}" HorizontalAlignment="Center" VerticalAlignment="Center" Foreground="White"/>
</Border>
</Border>
</Grid>
<Border Width="17" Height="17" BorderBrush="White" HorizontalAlignment="Center" VerticalAlignment="Center" CornerRadius="1" x:Name="numberContainer" Visibility="Collapsed">
<TextBlock x:Name="number" Text="80" HorizontalAlignment="Center" VerticalAlignment="Center" Foreground="White"/>
</Border>
</Grid>
</DataTemplate>
This is the code that create the Adorner :
if (this.draggedAdorner == null)
{
var adornerLayer = AdornerLayer.GetAdornerLayer(source);
this.draggedAdorner = new DraggedAdorner(draggedData, dataTemplate, source, adornerLayer);
}
And this is the code that init an adorner
public DraggedAdorner(List dragDropData, DataTemplate dragDropTemplate, FrameworkElement adornedElement, AdornerLayer adornerLayer)
: base(adornedElement)
{
this.adornerLayer = adornerLayer;
this.contentPresenter = new ContentPresenter();
this.contentPresenter.Content = dragDropData[0];
this.contentPresenter.ContentTemplate = dragDropTemplate;
this.adornerLayer.Add(this);
}
The draggedData, will be a list of MyType, I get the first item as the content of the ContentPresenter of my DraggedAdorner, so the DataTemplate can apply.
The problem is, I want to access the numberContainer and number control of the DataTemplate, in order to display the number of dragged object, in the adorner. But I cannot manage to access it, whatever I try, It ends with the "This operation is valid only on elements that have this template applied." message.
I have tought I could do something like this :
this.contentPresenter.ContentTemplate.FindName("number", this.contentPresenter);
Since the DataTemplate should apply to the ContentPresenter, but nope...
For information the adornedElement is the ListViewItem from which the drag occurs.
If you have any idea...

Answer 1

Ok, so I have found how to achieve what I wanted.
I don't know why it didn't comes to mind earlier, and why I didn't found anything about this before.
I have just added a single line before trying to access the template :
this.UpdateLayout()
Looks like it forces the ContentPresenter and DataTemplate object to be update and "re-rederend" so the ContentPresenter is really templated by my DataTemplate.