Question

I’m building a chart to show items by volume by category. So far I’ve been succcessful in showing items by volume as it’s a simple x/y chart, however I’d like to show y2 and I know MS Chart Controls has a built in AxisY2 however when I try anything with it the Chart get’s all funky.

Here’s what I’m looking for (in ascii art):

item1 |[][][][][].............| cat1
item2 |[][]...................| cat2
item3 |[][....................| cat1
item4 |[][][][][][][][........| cat1
      |_______________________|
        0   1   2   3   4   5

Like previously mentioned I can get Items and counts to show fine as that’s relatively easy, it’s the Categories that I can’t seem to place.

Thanks

Answer 1

Short Answer first : According to MS Examples, there is no straight way to do that, but just a workaround trick : Plot your series on a second chartArea matching exactly your existing area position, (by performing a copy of your Series) having invisible primary X/Y Axis and a visible secondary Y Axis (AxisY2). And set the chartArea and the copied series’s backcolors to transparent. (This can be applied to secondary X axis in case of column graphs rather that bars)

//Suppose you already have a ChartArea with the series plotted and the left Y Axis
//Add a fake Area where the only appearent thing is your secondary Y Axis
ChartArea area1 = chart.ChartAreas.Add("ChartAreaCopy_" + series.Name);
area1.BackColor = Color.Transparent;
area1.BorderColor = Color.Transparent;
area1.Position.FromRectangleF(area.Position.ToRectangleF());
area1.InnerPlotPosition.FromRectangleF(area.InnerPlotPosition.ToRectangleF());
area1.AxisX.MajorGrid.Enabled = false;
area1.AxisX.MajorTickMark.Enabled = false;
area1.AxisX.LabelStyle.Enabled = false;
area1.AxisY.MajorGrid.Enabled = false;
area1.AxisY.MajorTickMark.Enabled = false;
area1.AxisY.LabelStyle.Enabled = false;

area1.AxisY2.Enabled = AxisEnabled.True;
area1.AxisY2.LabelStyle.Enabled = true;

// Create a copy of specified series, and change Y Values to categories
Series seriesCopy = chart.Series.Add(series.Name + "_Copy");
seriesCopy.ChartType = series.ChartType;
foreach(DataPoint point in series.Points)
{
    double category = getYourItemCategory(point.XValue);
    seriesCopy.Points.AddXY(point.XValue, category);
}

// Hide copied series
seriesCopy.IsVisibleInLegend = false;
seriesCopy.Color = Color.Transparent;
seriesCopy.BorderColor = Color.Transparent;

//Drop it in the chart to make the area show (only the AxisY2 should appear)
seriesCopy.ChartArea = area1.Name;

PS : I’ve spent two nights awake messing with MS chart controls, trying to put two different Y axis on a Chart Area. I wanted to put two differently scaled series (same X scale, different Y Scales : one on the left for Series A , the other on the right for Series B).
In fact, this proved to be a real nightmare, when one could expect this to be pretty straightforward. The truth is that MS Chart Controls are definitely NOT adapted for this particular use case IMHO. The multiple Y axis sample suggested in the MSCC sample examples is an awful and very ugly workaround, which requires two chartareas on top of the default one, playing with visibility and transparency, to achieve the desired effect (which sounds like a very bad illusion magic trick).

While hoping for this to be enriched and fixed in a proper way in future versions, if you really need an efficient way to manage multiple Y-Axis, sitck to ZedGraph