How to drag and drop chart series points at runtime in WinForms Chart?

To enable dragging and repositioning of chart series points in WinForms Charts, you can calculate new X and Y values during ChartRegionMouse Events such as MouseUp, MouseDown, and MouseMove. These new X and Y values are derived from the mouse coordinates using the GetValueByPoint method, which returns the chart's data values corresponding to the mouse position.

C#

private int seriesIndex = -1;
private int selectedIndex = -1;
private bool isSelected = false;

this.chartControl1.ChartRegionMouseDown += ChartControl1_ChartRegionMouseDown;
this.chartControl1.ChartRegionMouseMove += ChartControl1_ChartRegionMouseMove;
this.chartControl1.ChartRegionMouseUp += ChartControl1_ChartRegionMouseUp;

private void ChartControl1_ChartRegionMouseDown(object sender, ChartRegionMouseEventArgs e)
{
    if (e.Region != null && e.Region.IsChartPoint)
    {
        seriesIndex = e.Region.SeriesIndex;
        selectedIndex = e.Region.PointIndex;
        isSelected = true;
    }
}

private void ChartControl1_ChartRegionMouseMove(object sender, ChartRegionMouseEventArgs e)
{
    if (isSelected && seriesIndex != -1 && selectedIndex != -1)
    {
        double newY = this.chartControl1.ChartArea.GetValueByPoint(e.Point).YValues[0];
        this.chartControl1.Series[seriesIndex].Points[selectedIndex].YValues[0] = newY;
        this.chartControl1.Refresh();
    }
}

private void ChartControl1_ChartRegionMouseUp(object sender, ChartRegionMouseEventArgs e)
{
    if (isSelected)
    {
        isSelected = false;
        this.chartControl1.Redraw(true);
        selectedIndex = -1;
        seriesIndex = -1;
    }
}

VB

Private seriesIndex As Integer = -1
Private selectedIndex As Integer = -1
Private isSelected As Boolean = False

AddHandler lineChart.ChartRegionMouseDown, AddressOf ChartControl1_ChartRegionMouseDown
AddHandler lineChart.ChartRegionMouseMove, AddressOf ChartControl1_ChartRegionMouseMove
AddHandler lineChart.ChartRegionMouseUp, AddressOf ChartControl1_ChartRegionMouseUp

Private Sub ChartControl1_ChartRegionMouseDown(sender As Object, e As ChartRegionMouseEventArgs)
    If e.Region IsNot Nothing AndAlso e.Region.IsChartPoint Then
        seriesIndex = e.Region.SeriesIndex
        selectedIndex = e.Region.PointIndex
        isSelected = True
    End If
End Sub

Private Sub ChartControl1_ChartRegionMouseMove(sender As Object, e As ChartRegionMouseEventArgs)
    If isSelected AndAlso seriesIndex <> -1 AndAlso selectedIndex <> -1 Then
        Dim newY As Double = lineChart.ChartArea.GetValueByPoint(e.Point).YValues(0)
        lineChart.Series(seriesIndex).Points(selectedIndex).YValues(0) = newY
        lineChart.Refresh()
    End If
End Sub

Private Sub ChartControl1_ChartRegionMouseUp(sender As Object, e As ChartRegionMouseEventArgs)
    If isSelected Then
        isSelected = False
        lineChart.Redraw(True)
        selectedIndex = -1
        seriesIndex = -1
    End If
End Sub