I'm trying to do something simple -- make a DependencyProperty and then bind to it. However, the getter doesn't appear to fire when I start up the app. (I'm guessing the solution will make me smack my head and go "Doh!", but still. :) )

Any ideas?

Code-behind code:

public static readonly DependencyProperty PriorityProperty = 
        DependencyProperty.Register("Priority", 
        typeof (Priority), typeof (PriorityControl), null);

public Priority Priority
{
    get { return (Priority)GetValue(PriorityProperty); }
    set { SetValue(PriorityProperty, value); }
}

Control XAML:

<ListBox Background="Transparent" 
         BorderThickness="0" 
         ItemsSource="{Binding Path=Priorities}" 
         Name="PriorityList" 
         SelectedItem="{Binding Path=Priority, Mode=TwoWay}">
  <ListBox.ItemTemplate>
    <DataTemplate>
        <Grid Height="16" Width="16">
          <Border BorderBrush="Black"
                  BorderThickness="2"
                  CornerRadius="3"
                  Visibility="{Binding RelativeSource=
                       {RelativeSource Mode=FindAncestor, AncestorType=ListBoxItem}, Path=IsSelected, Converter={StaticResource boolToVisibilityConverter}}" />
          <Border CornerRadius="3" Height="12" Width="12">
            <Border.Background>
              <SolidColorBrush Color="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=ListBoxItem}, Path=Content, Converter={StaticResource priorityToColorConverter}}" />
            </Border.Background>
          </Border>
        </Grid>
    </DataTemplate>
   </ListBox.ItemTemplate>
   <ListBox.ItemsPanel>
     <ItemsPanelTemplate>
       <StackPanel Orientation="Horizontal"/>
     </ItemsPanelTemplate>
   </ListBox.ItemsPanel>
 </ListBox>

Binding statement:

<UI:PriorityControl Grid.Column="8" 
                    Priority="{Binding Path=Priority}" 
                    VerticalAlignment="Center"/>

Some other notes:

• Binding is in a UserControl
• UserControl contains the PriorityControl
• PriorityControl contains the DependencyProperty
• I've checked that the data the UserControl is getting the appropriate data -- every other binding works.
• If I change the selection on the PriorityControl via the mouse, everything fires as appropriate. It's just that initial setting of the value that isn't working.
• Priority is an enum.