The FunctionBindingBehavior allows you to use a ViewModel function to calculate a control property. The example uses this behavior to bind the ChartControl to the GetFilteredItems function and pass SelectionRangeStart and SelectionRangeEnd properties of the RangeControl to the function.
public IList<DataItem> GetFilteredItems(DateTime start, DateTime end) {
return this.Points.Where(x => x.Date.Date >= start && x.Date.Date <= end).OrderByDescending(x => x.ValueSummary).ToList();
}