Amy Gray Amy Gray - 30 days ago 9
C# Question

Dundas Charting C# conditional colour rules on column

I am using Dundas Charts in Visual Studio using C#.

I have a chart with one series - the chart is displaying the series on columns. I am currently using the following code to add the series:

public void AddSeries(string name, SeriesChartType type, IEnumerable xValues, IEnumerable yValues, bool showLabels = true)
Series s = new Series();
s.Points.DataBindXY(xValues, yValues);
s.LegendText = name;
s.Type = type;
if (type == SeriesChartType.Line) s.Color = Color.FromArgb(139,0,0);
else s.Color = _palette[_chart.Series.Count < _palette.Length ? _chart.Series.Count : 0];
s.ShowLabelAsValue = showLabels;
s.FontAngle = -90;
s.LabelFormat = string.IsNullOrWhiteSpace(_chart.ChartAreas["Default"].AxisY.LabelStyle.Format) ? "P0" : _chart.ChartAreas["Default"].AxisY.LabelStyle.Format;
s.Font = new Font("Arial", 5);


I would like to change the colour of each column depending on the value for that column - this will be based on a int target value.
For example, if the column is less than our target value, it should display red, else it should display green.

How would you recommend doing this?

Answer Source

I have found a suitable answer for this, the only issue I have with this solution is that the columns come out in varying widths depending on the number of points on the x axis.

    void GetColourCodedSeries(ChartHelper chartHelper, DataTable table, string groupingColumn, string valueColumn)
        List<Color> _palette = new List<Color>();

        var x = table.AsEnumerable().Select(f => f.Field<string>(groupingColumn)).ToArray();

        foreach (DataRow row in table.Rows)
            if (Convert.ToDecimal(row[valueColumn].ToString()) >= _availabilityTarget) _palette.Add(Color.FromArgb(0, 176, 80));
            else _palette.Add(Color.FromArgb(139, 0, 0));

            List<decimal?> y = new List<decimal?>();

            foreach(var value in x)
                if (value == row[groupingColumn].ToString()) y.Add(Convert.ToDecimal(row[valueColumn].ToString()));
                else y.Add(null);

            chartHelper.AddSeries(SeriesChartType.Column, x, y, _palette.ToArray());

This code creates a dynamic colour palette for the columns based on the values. I then add one series per row in my table, when adding the series I am including all of the possible x values and 1 y value per each of these - however, only one of the y axis values has an actual value, all of the others are marked as null values (i did try using 0 values but this made the chart look very messy).