Commented Unassigned: RichTextBox + RichTextBoxFormatBar throwing a NullReference exception when dragged, possible bug? [21943]

Hello,

I am not sure why but I am receiving the following exception when I select text then attempt to drag the attached RichTextBoxFormatBar:
```
Object reference not set to an instance of an object.
at Xceed.Wpf.Toolkit.RichTextBoxFormatBar.ProcessMove(DragDeltaEventArgs e)
at Xceed.Wpf.Toolkit.RichTextBoxFormatBar.DragWidget_DragDelta(Object sender, DragDeltaEventArgs e)
at System.Windows.Controls.Primitives.DragDeltaEventArgs.InvokeEventHandler(Delegate genericHandler, Object genericTarget)
at System.Windows.RoutedEventArgs.InvokeHandler(Delegate handler, Object target)
at System.Windows.RoutedEventHandlerInfo.InvokeHandler(Object target, RoutedEventArgs routedEventArgs)
at System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised)
at System.Windows.UIElement.RaiseEventImpl(DependencyObject sender, RoutedEventArgs args)
at System.Windows.UIElement.RaiseEvent(RoutedEventArgs e)
etc.... etc...
```

Looking at the source code for RichTextBoxFormatBar: http://wpftoolkit.codeplex.com/SourceControl/latest#Main/Source/ExtendedWPFToolkitSolution/Src/Xceed.Wpf.Toolkit/RichTextBoxFormatBar/RichTextBoxFormatBar.cs

The code for ProcessMove():
```
private void ProcessMove( DragDeltaEventArgs e )
{
AdornerLayer layer = AdornerLayer.GetAdornerLayer( Target );
UIElementAdorner<Control> adorner = layer.GetAdorners( Target )[ 0 ] as UIElementAdorner<Control>;
adorner.SetOffsets( adorner.OffsetLeft + e.HorizontalChange, adorner.OffsetTop + e.VerticalChange );
}
```

It appears that maybe (I have not built the source myself) the call to AdornerLayer.GetAdornerLayer(Target) is failing to return a value... So I was wondering if there is something I might be missing in my view XAML to get it working correctly?

```
<Toolkit:RichTextBox DockPanel.Dock="Right"
Text="{Binding Query, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}">
<Toolkit:RichTextBox.Style>
<Style TargetType="{x:Type Toolkit:RichTextBox}">
... (Note have tried removing the custom style, did not resolve the issue) ...
</Style>
</Toolkit:RichTextBox.Style>
<Toolkit:RichTextBox.TextFormatter>
<TextFormatting:RtfToHtmlFormatter></TextFormatting:RtfToHtmlFormatter>
</Toolkit:RichTextBox.TextFormatter>
<Toolkit:RichTextBoxFormatBarManager.FormatBar>
<Toolkit:RichTextBoxFormatBar></Toolkit:RichTextBoxFormatBar>
</Toolkit:RichTextBoxFormatBarManager.FormatBar>
</Toolkit:RichTextBox>
```

Also is there a way to use the RichTextBoxFormatBar with dragging disabled for the meantime?

Thanks,
Alex.
Comments: ** Comment from web user: alex21 **

Lastly I just noticed this is because I added field validation errors to the property bound to "Text" which was causing the Validation.ErrorTemplate to show introducing the other layer preventing the UIElementAdorner<Control> from being found.

So I am 100% this is a bug now, but in the meantime I have just removed the field validation and placed an error message to the right of the control.