How to fill the area between two series in MS Chart

Question

I am populating chart data under timer Tick event:

private void Timer_Tick(object sender, EventArgs e)
{ 
    Chart1.Series["Series2"].Points.AddY(17);
    Chart1.Series["Series3"].Points.AddY(10);
}

Which generates two series like this:

I'd like to fill the area between the series like this:

Here is the designer code for the chart:

chartArea1.BackColor = System.Drawing.Color.Black;
chartArea1.Name = "ChartArea1";
this.chart1.ChartAreas.Add(chartArea1);
legend1.Name = "Legend1";
this.chart1.Legends.Add(legend1);
this.chart1.Location = new System.Drawing.Point(72, 339);
this.chart1.Name = "chart1";
series1.ChartArea = "ChartArea1";
series1.ChartType = System.Windows.Forms.DataVisualization.Charting.SeriesChartType.Spline;
series1.Color = System.Drawing.Color.Red;
series1.Legend = "Legend1";
series1.Name = "Series1";
series2.ChartArea = "ChartArea1";
series2.ChartType = System.Windows.Forms.DataVisualization.Charting.SeriesChartType.Spline;
series2.Color = System.Drawing.Color.Aqua;
series2.Legend = "Legend1";
series2.Name = "Series2";
this.chart1.Series.Add(series1);
this.chart1.Series.Add(series2);

Answer 1

You can handle the Paint event of the chart and get the points of each series, then create a path based on those points and fill the path:

Axis.ValueToPixelPosition is the method which helps you to translate series point to paint surface point.

Example - Filling the space between two series

The following example, creates two series: Sin(α) and 2×Sin(α) and fills the area between the two charts with Pink color:

private void Chart1_Paint(object sender, PaintEventArgs e)
{
    e.Graphics.SmoothingMode = SmoothingMode.AntiAlias;
    var points0 = chart1.Series[0].Points.Select(p =>
        new PointF(
            (float)chart1.ChartAreas[0].AxisX
            .ValueToPixelPosition(p.XValue),
            (float)chart1.ChartAreas[0].AxisY
            .ValueToPixelPosition(p.YValues[0]))).ToArray();
    var points1 = chart1.Series[1].Points.Select(p =>
        new PointF(
            (float)chart1.ChartAreas[0].AxisX
            .ValueToPixelPosition(p.XValue),
            (float)chart1.ChartAreas[0].AxisY
            .ValueToPixelPosition(p.YValues[0]))).ToArray();
    using (var path = new GraphicsPath())
    {
        path.StartFigure();
        path.AddCurve(points0);
        path.AddCurve(points1.Reverse().ToArray());
        path.CloseFigure();
        path.FillMode = FillMode.Alternate;
        using (var brush = new SolidBrush(Color.Pink))
            e.Graphics.FillPath(brush, path);
    }
}

private void Form1_Load(object sender, EventArgs e)
{
    chart1.Series.Clear();
    chart1.ChartAreas.Clear();

    chart1.ChartAreas.Add("A1");
    chart1.ChartAreas[0].AxisX.Minimum = 0;
    chart1.ChartAreas[0].AxisX.Interval = 90;

    chart1.Series.Add("Sin(α)");
    chart1.Series[0].ChartType =
        System.Windows.Forms.DataVisualization.Charting.SeriesChartType.Spline;
    chart1.Series[0].Color = Color.Blue;
    chart1.Series[0].BorderWidth = 3;

    chart1.Series.Add("2×Sin(α)");
    chart1.Series[1].ChartType =
        System.Windows.Forms.DataVisualization.Charting.SeriesChartType.Line;
    chart1.Series[1].Color = Color.Red;
    chart1.Series[1].BorderWidth = 3;

    for (int i = 0; i < 360; i++)
        chart1.Series[0].Points.AddXY(i, Math.Sin(i * Math.PI / 180));
    for (int i = 0; i < 360; i++)
        chart1.Series[1].Points.AddXY(i, 2 * Math.Sin(i * Math.PI / 180));

    chart1.Paint += Chart1_Paint;
}