Create an Excel Line – Column combination chart in C#, revisited

I wrote a post a few days ago describing how to generate a Line – Column chart in Excel through C#. And then a few things happened. Jon Peltier proposed a much nicer approach, I realized that my code worked for Excel 2003 but not Excel 2007, and someone asked for my code, “Jon-Peltier style”. So here we go: assuming your chart has more than one series, and you want the second series to be formatted as a line, all the rest as columns, you would do something like this:

// Create your chart object first
// formatted as column
Chart chart = ExcelCharts.AddChart(targetWorkbook, my chart, the chart title, XlChartType.xlColumnClustered, dataRange, XlRowCol.xlRows);
// Select the second series and make it a line
Series series = (Series)chart.SeriesCollection(2);
series.ChartType = XlChartType.xlLine;

Here is a simplified version of my AddChart method, which creates the base chart. Nothing fancy, but gets the job done.

public static Excel.Chart AddChart(Workbook workbook, string chartSheetName, string title, XlChartType chartType, Range dataRange, XlRowCol byRowOrCol)
    Excel.Chart chart;
    chart = (Excel.Chart)workbook.Charts.Add(Type.Missing, Type.Missing, Type.Missing, Type.Missing);
    chart.ChartType = chartType;
    chart.Location(XlChartLocation.xlLocationAsNewSheet, chartSheetName);
    chart.SetSourceData(dataRange, byRowOrCol);
    chart.HasTitle = true;
    chart.ChartTitle.Text = title;
    return chart;

As an aside, I was not happy with myself when I realized the code didn’t run on Excel 2007. I tend to write Excel-related code against Excel 2003 first, assuming it is the smallest common denominator and will likely work with Excel 2007 – but this is a perfect illustration that while it will typically be correct, it will sometimes fail, sometimes in very unexpected and trivial places, like in this example. Moral of the story: as Lenin allegedly said, “Trust is good, control is better”…

