MS Chart cursor position not linked to X data

Question

I have an MS chart that is showing logarithmic frequency data in my c# app. I want to use a cursor to select a data point. Since the cursor doesn't automatically snap to the closest data point, I had to write a routine that would do that for me.

private void chart_CursorPositionChanged(object sender, CursorEventArgs e)
        {
            if (double.IsNaN(e.NewPosition)) return;

            if (chart.ChartAreas[0].CursorX.IsUserEnabled)
            {
                double coercedPosition = chart.Series[0].Points.Aggregate((x, y) => Math.Abs(x.XValue - e.NewPosition) < Math.Abs(y.XValue - e.NewPosition) ? x : y).XValue;
                //move the cursor to the closest point
                chart.ChartAreas[0].CursorX.Position = coercedPosition;
                txtZPrime.Text = SelectedStep.GetZatFreq(coercedPosition).ToString();
            }
        }

The problem is, when the cursor is moved, and I get the position of the cursor, the position is not the position of the cursor in the X data line. Instead, it's the number of major divisions from the left of the chart.

I made sure the data is charting correctly and the labels are correct for the X axis, but the cursor position is not correlated to the X data.

Any ideas what's the problem?

Thanks

Answer

Hi NathanSmith-2125,
Please try to use Axis.PixelPositionToValue(Double) method to convert an absolute pixel position along an axis to an axis value.

chart.ChartAreas[0].CursorX.Position =chart.ChartAreas[0].AxisX.PixelPositionToValue(coercedPosition);

And note that this method only works in paint events.
Best Regards,
Daniel Zhang

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MS Chart cursor position not linked to X data

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