How to add a text on top of a column with ZedGraph?

Question

How can I add some text on top of a bar in a chart. This is the code I have to add the bar:

var color = ColorTranslator.FromHtml(row.Colour);
var barItem = graphPane.AddBar(row.Propensity.ToString(), null, Ys.ToArray(), color);

Thank you

Answer 1

Here is a quick example using TextObj to simply add labels to each bar.

GraphPane myPane = zedGraphControl1.GraphPane;

double[] y = { 100, 50, 75, 125 };

BarItem myBar = myPane.AddBar("Data", null, y, Color.Red);
for (int i = 0; i < myBar.Points.Count; i++)
{
    TextObj barLabel = new TextObj(myBar.Points[i].Y.ToString(), myBar.Points[i].X, myBar.Points[i].Y + 5);
    barLabel.FontSpec.Border.IsVisible = false;
    myPane.GraphObjList.Add(barLabel);
}

myBar.Label.IsVisible = true;

zedGraphControl1.AxisChange();
zedGraphControl1.Invalidate();

Of course this just uses the value of the data as the label. If you wanted to use custom labels, you could create a string array or list and use that inside the loop.

Here are some ZedGraph references:

• Introduction and examples: http://www.codeproject.com/KB/graphics/zedgraph.aspx
• Source code documentation: http://zedgraph.sourceforge.net/documentation/default.html

Answer 2

You need to define AlignH and AlignV in your text object:

TextObj textLabel = new TextObj(value.ToString(), positionX, value, CoordType.AxisXYScale, AlignH.Center, AlignV.Top);

AlignV define the position of your value on the bar.

Answer 3

Providing you want the label text to match the value of each bar, then you can do it with a single line of code:

BarItem.CreateBarLabels(graphPane, false, "F0");

Note that the 3rd parameter is a double.ToString format. e.g. "F0" = 12, "F2" = 12.34

However, if you want any flexibity with it then this solution is not ideal. It also doesn't work very well if you have a stacked bar chart, because having any 0 value data will cause labels to overlap and look horrific