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));
}