OnPropertyChangedCallback not being invoked when using an attached property - wpf

Question

My OnPropertyChangedCallback is not being called for an attached property.
I expect this method to be called by default when running the app.
My code compiles.
I have no errors in the Output window.
Any suggestions?
Attached Property:
namespace FileModifier.Behaviors
{
public class AttachedProperties : DependencyObject
{
public static readonly DependencyProperty TextProperty =
DependencyProperty.Register("Text", typeof(string), typeof(AttachedProperties), new PropertyMetadata(null, OnPropertyChangedCallback));
public static void SetText(DependencyObject d, string value)
{
d.SetValue(TextProperty, value);
}
public static string GetText(DependencyObject d)
{
return d.GetValue(TextProperty) as string;
}
private static void OnPropertyChangedCallback(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
var richEditBox = d as RichTextBox;
var textRange = new TextRange(richEditBox.Document.ContentStart, richEditBox.Document.ContentEnd);
throw new NotImplementedException();
}
}
}
XAML:
<RichTextBox x:Name="FileContentControl" IsReadOnly="True"
behaviors:AttachedProperties.Text="{Binding ElementName=FileListView, Path=SelectedItem,
Converter={StaticResource FilePathToContentConverter}}"
VerticalAlignment="Center" Padding="10" />
.
.
.
<ListView x:Name="FileListView" ItemsSource="{Binding FilePaths}" Grid.Column="2" Grid.Row="0"
SelectedItem="{Binding SelectedFilePath}"
VerticalAlignment="Center"
Margin="5">
<ListView.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding Converter={StaticResource TextTruncationConverter}}" />
</DataTemplate>
</ListView.ItemTemplate>
<ListView.ItemContainerStyle>
<Style TargetType="ListBoxItem">
<Setter Property="Foreground" Value="Blue" />
<Setter Property="Padding" Value="5" />
</Style>
</ListView.ItemContainerStyle>
</ListView>

Answer 1

You do not register attached property but normal DependencyProperty. You should use DependencyProperty.RegisterAttached instead. Also if your class contains only attached properties it may as well be static class. It does not have to inherit from DependencyObject
public static class AttachedProperties
{
public static readonly DependencyProperty TextProperty =
DependencyProperty.RegisterAttached("Text", typeof(string), typeof(AttachedProperties), new PropertyMetadata(null, OnPropertyChangedCallback));
public static void SetText(DependencyObject d, string value)
{
d.SetValue(TextProperty, value);
}
public static string GetText(DependencyObject d)
{
return d.GetValue(TextProperty) as string;
}
private static void OnPropertyChangedCallback(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
var richEditBox = d as RichTextBox;
var textRange = new TextRange(richEditBox.Document.ContentStart, richEditBox.Document.ContentEnd);
throw new NotImplementedException();
}
}