Change DependencyProperty value inside PropertyChangedCallback for this DependencyProperty

Question

I have a control with ComboBox:

<ComboBox x:Name="TraceComboBox"
          ItemsSource="{Binding SingleChannelList}" 
          SelectedItem="{Binding RelativeSource={RelativeSource  FindAncestor,
                         AncestorType={x:Type cc:LogicTriggerSimpleLevelControl}},
                         Path=SelectedTrace, Mode=TwoWay}">

Here PropertyChangedCallbackfor a property SelectedTracein an OuterControl containing ComboBox:

private static void OnSelectedTraceChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
    OuterControl oc = d as OuterControl ;
    oc.UpdateSelectedTrace();
}

private void UpdateSelectedTrace()
{
    ViewModelType vm = DataContext as ViewModelType;
    if (vm != null)
    {
        if (vm.SingleChannelList != null)
        {
            SelectedTrace = vm.SingleChannelList[0];
        }
    }
}

By my logic, the following should happen:

ComboBox (SingleChannelList[2]), . UpdateSelectedTrace(). SelectedTrace, , SingleChannelList[2]. UpdateSelectedTrace() SelectedTrace 1- (SingleChannelList[0]), , . "SelectedTrace" SingleChannelList [0], ComboBox SingleChannelList [0] .

, , :

SelectedTrace SingleChannelList[0], ComboBox SingleChannelList[2] . UpdatingTarget BindingExpression, , SelectedTrace SingleChannelList[0], ComboBox SingleChannelList[2]. , . - , ?

Answer 1

" ". "" . :

Answer 2

, WPF. propertychanged (, ), , . , IdentityConverter (ValueConverter, , ) Binding.