Question

For my project, I need to add and update real-time data to my dual y-axis graph. The Y and Y2 values share the same X value, and I created it already. Now I have a function that adds the new point pairs to the curve lists.

Here is my problem: My Y and Y2 values are always added to the curve list of the first curve. How can I get the Y2 value added to the second curve list in my graph?

Here is my function code:

    private void AddDataToGraph(ZedGraphControl zg1, XDate xValue, double yValue1, double yValue2)
    {
        // Make sure that the curvelist has at least one curve.
        if (zg1.GraphPane.CurveList.Count <= 0)
            return;

        // Get the first CurveItem in the graph.
        LineItem curve = zg1.GraphPane.CurveList[0] as LineItem;

        if (curve == null)
            return;

        // Get the PointPairList.
        IPointListEdit list = curve.Points as IPointListEdit;
        IPointListEdit list2 = curve.Points as IPointListEdit;

        // If this is null, it means the reference at curve.Points does not
        // support IPointListEdit, so we won't be able to modify it.
        if (list == null || list2 == null)
            return;

        // Add new data points to the graph.
        list.Add(xValue, yValue1);
        list2.Add(xValue, yValue2);

        // Force redraw.
        zg1.Invalidate();
    }

How can he Y2 values be added to the 2nd curve list?

Answer 1

Found a possible solution myself. Here are my code changes:

private void AddDataToGraph(ZedGraphControl zg1, XDate xValue, double yValue1, double yValue2)
    {
        // Make sure that the curvelist has at least one curve
        if (zg1.GraphPane.CurveList.Count <= 0)
            return;

        // Get the first CurveItem in the graph
        LineItem curve = zg1.GraphPane.CurveList[0] as LineItem;
        LineItem curve2 = zg1.GraphPane.CurveList[1] as LineItem;

        if (curve == null || curve2 == null)
            return;

        // Get the PointPairList
        IPointListEdit list = curve.Points as IPointListEdit;
        IPointListEdit list2 = curve2.Points as IPointListEdit;
        // If this is null, it means the reference at curve.Points does not
        // support IPointListEdit, so we won't be able to modify it
        if (list == null || list2 == null)
            return;

        // add new data points to the graph
        list.Add(xValue, yValue1);
        list2.Add(xValue, yValue2);

        // force redraw
        zg1.Invalidate();
    }

The important thing is to use the index in the “CurveList[i]”. So [0] is my curve with the Y values and [1] is my curve with the Y2 values, and so on.

I hope this helps anybody who has the same or similar problem.