From the code that you have provided (chart.Series) it seems that you are talking about the RadChartView and not the RadChart control. This is why I have changed the product of this thread. Let me know if I have made a mistake.
Now, onto your question. The chart not getting updated is expected because double is not an observable collection. You will either need to reset the ItemsSource every time you need the chart to update or use an observable collection instead:
chart.Series.ItemsSource = tempDrw;
var oc =
chart.Series.ItemsSource = oc;
All the best,
the Telerik team