Thanks for your reply.

because of implementing dragging the data point in this line chart, it didn't bind any datasource, in other words, it program added series and datapoints.

I referred to DraggingDataPointTool.cs in the local sample code to implement this dragging function, and when I bound to datasource, this function doesn't work.

could you provide the example for how to drag the data point when it bound to a datasource?

Ok, so you're using a LineChart with a NumericSeries. If that's the case, you must be supplying strings as your labels, even though they appear to be numeric. So, your data really looks more like ("7500", 16.1), ("7600", 10.2), ("7700", 19.9). Strings can't really be sorted like numbers by the Sort method, so you have to implement your own sorting.

Here's an example.

ultraChart1.ChartType = ChartType.LineChart;
NumericSeries series = new NumericSeries();
series.Points.Add(new NumericDataPoint(2, "40", false));
series.Points.Add(new NumericDataPoint(5, "60", false));
series.Points.Add(new NumericDataPoint(8, "80", false));
series.Points.Add(new NumericDataPoint(10, "70", false));

for (int i = 0; i < series.Points.Count; i++)
{
 for (int j = i + 1; j < series.Points.Count; j++)
 {
  double val1 = Double.Parse(series.Points[i].Label);
  double val2 = Double.Parse(series.Points[j].Label);
  if (val1 > val2)
  {
   NumericDataPoint temp = series.Points[i];
   series.Points[i] = series.Points[j];
   series.Points[j] = temp;
  }
 }
}

ultraChart1.Series.Add(series);

After I use mySeries.Points.Sort(), it sort the values of Y-Axis, not the labels in X-Axis.

the type of my labels in X-Axis is the numeric.

Could you please tell me how to sort the labels in X-Axis? 

Thanks a lot.

Actually, turns out that numeric data point collection does implement sorting, so you should be able to use mySeries.Points.Sort() to arrange your points. Let me know if that works for you.