private void FunctionHistoryChartView_DataContextChanged(object sender, DependencyPropertyChangedEventArgs e)
        {
            FunctionSummaryViewModel vm = DataContext as FunctionSummaryViewModel;

            if (vm != null)
            {
                vm.OnChanged += Update;
            }
        }
        public void Update()
        {
            FunctionSummaryViewModel vm = DataContext as FunctionSummaryViewModel;

            if (vm != null && vm.Stats != null)
            {
                Chart.IsAutoFitEnabled = true;
                WorkChart.PlotY(vm.Stats.Samples.Select(s => s.Work));
                WaitChart.PlotY(vm.Stats.Samples.Select(s => s.Wait));
            }
            else
            {
                WorkChart.Plot(Array.Empty <double>(), Array.Empty <double>());
                WaitChart.Plot(Array.Empty <double>(), Array.Empty <double>());
            }
        }