Binding in CustomControl

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开发者_开发问答 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!