Would like to place a vertical line at a certain datetime value against the CategoryDateTimeXAxis

So far no luck...

GetScaledValue does not return anything reasonable

Xaml:

<ig:ValueOverlay Axis="{Binding ElementName=xmXAxis}" Thickness="1" Brush="Red">

  <ig:ValueOverlay.Value>

   <MultiBinding Converter="{StaticResource DateTimeConverter}">

      <Binding Path="DateValue"/>

      <Binding ElementName="xmXAxis"/>

   MultiBinding>

  ig:ValueOverlay.Value>

 ig:ValueOverlay> 

Codebehind

public class DateTimeConverter : IMultiValueConverter

{

    public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)

        {

      if (values[0] != null && values[0] is DateTime)

            {

                  var axis = values[1] as CategoryDateTimeXAxis;

                 if (axis != null)

                 {

                       //return ((DateTime)values[0]).Ticks;

           var chart = axis.SeriesViewer;

                       return axis.GetScaledValue(((DateTime)values[0]).Ticks, chart.WindowRect, chart.ViewportRect);

                }

            }

      return null;

        }

    public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)

        {

              throw new NotImplementedException();

        }

    }

Thanks