Binding in CustomControl - wpf

Question

I have created a custom control which is (among other things) able to display many expanders in an ItemsControl.
<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:sys="clr-namespace:System;assembly=mscorlib"> <Style TargetType="{x:Type NxTabControl:NxCategoryControl}">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type NxTabControl:NxCategoryControl}">
<ScrollViewer x:Name="contentScrollViewer" HorizontalScrollBarVisibility="Disabled" VerticalScrollBarVisibility="Auto">
<StackPanel HorizontalAlignment="Stretch" DockPanel.Dock="Bottom" VerticalAlignment="Stretch" Background="Transparent">
<ItemsControl ItemsSource="{TemplateBinding Content}">
<ItemsControl.Template>
<ControlTemplate TargetType="ItemsControl">
<Border>
<ItemsPresenter/>
</Border>
</ControlTemplate>
</ItemsControl.Template>
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<StackPanel Orientation="Vertical" />
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
</ItemsControl>
</StackPanel>
</ScrollViewer>
</DockPanel>
</Border>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style> </ResourceDictionary>
The ItemsControl is binding to :
ItemsSource="{TemplateBinding Content}
Which is a DP in the class:
public class CategoryControl : ItemsControl
{
public ObservableCollection<Expander> Content
{
get { return (ObservableCollection<Expander>)GetValue(ContentProperty); }
set { SetValue(ContentProperty, value); }
}
public static readonly DependencyProperty ContentProperty = DependencyProperty.Register("Content", typeof(ObservableCollection<Expander>), typeof(CategoryControl), new FrameworkPropertyMetadata(new ContentCollection(), FrameworkPropertyMetadataOptions.AffectsRender | FrameworkPropertyMetadataOptions.AffectsParentMeasure)); }
I am using my custom control in a user Control by setting the content Property and adding expanders to it:
<NxTabControl:NxCategoryControl x:Name="catControl" DockMode="Top" HorizontalAlignment="Stretch" VerticalAlignment="Stretch" BorderBrush="Green">
<TabControl:CategoryControl.Content>
<Expander Margin="0 3 0 3" IsExpanded="True" Header="Adresse" >
<ScrollViewer x:Name="ScrollViewerAdresse" HorizontalAlignment="Stretch" ockPanel.Dock="Left">
<Grid Width="{Binding ElementName=ScrollViewerAdresse, Path=ActualWidth, Converter={StaticResource HalfWidthConverter}}">
</Grid>
</ ScrollViewer>
</Expander>
<Expander>
</Expander>
<Expander Header={Binding ExpanderHeader}>
</Expander>
</TabControl:CategoryControl.Content>
My problem in this context is that I am not able to set this binding:
Grid Width="{Binding ElementName=ScrollViewerAdresse, Path=ActualWidth}"
And also no other binding that goes to an “ElementName”. I am e.g also binding to XamDataGrids.ActiveRecords by their name and other Elements. None of the bindings works.
Snoop tells me for the Width Property of the Grid:
System.Windows.Data Error: 4 : Cannot find source for binding with reference 'ElementName=ScrollViewerAdresse'.
BindingExpression:Path=ActualWidth; DataItem=null; target element is 'Grid'; target property is 'Width' (type 'Double')
Other bindings I am using in my expanders, binding to the ViewModel of the usercontrol work though, e.g.:
Header={Binding ExpanderHeader}
Any help would be welcome! Thx!