private static void SmoothDownPropertyChangedAction(ScrollViewer sv, double value)
 {
     Nullable<double> smcsrvalue = ScrollViewerBehaviour.GetSmoothScrolling(sv);
     if (smcsrvalue.HasValue)
     {
         value = value * smcsrvalue.Value;
     }
     sv.SmoothToVertical(sv.VerticalOffset + value, TimeSpan.FromSeconds(0.05));
 }