How can I set the Data Label position for an Excel pie chart using C#?

Question

I am creating an Excel export that contains several pie charts which are dynamically created based on data from a database that is dumped into a range of cells within the spreadsheet. I need the data labels for the pie charts to be on the outside end of the pie chart. The data labels by default are set to best fit.

I have tried to manipulate the data label positions with eLabelPosition which has an OutEnd property but have had no luck. Doing this causes the data labels to completely disappear.

Below is the method I am using to generate my pie charts.

    private void AddPieChart(ExcelWorksheet worksheet, int firstDataRow, int firstDataColumn, int lastDataRow, int nextColumn, int firstColumn)
    {
        ExcelPieChart pieChart = worksheet.Drawings.AddChart(worksheet.Name.ToString() + " Pie Chart", eChartType.Pie3D) as ExcelPieChart;
        var serie = pieChart.Series.Add(ExcelCellBase.GetAddress(firstDataRow + 3, firstDataColumn, lastDataRow + 3, firstDataColumn),
                                        ExcelCellBase.GetAddress(firstDataRow + 3, firstColumn, lastDataRow + 3, firstColumn));

        pieChart.DataLabel.ShowCategory = true;
        pieChart.DataLabel.ShowLeaderLines = true;
        pieChart.DataLabel.Font.Bold = true;
        pieChart.DataLabel.Font.Size = 12;
        pieChart.Legend.Remove();
        pieChart.SetSize(500, 350);
        pieChart.SetPosition(lastDataRow + 5, 0, nextColumn - 1, 0);
        pieChart.Border.Fill.Color = Color.White;
        pieChart.Series.Chart.RoundedCorners = false;

        var pieSerie = (ExcelPieChartSerie)serie;
        pieSerie.DataLabel.Position = eLabelPosition.OutEnd;
    }

Answer 1

It appears that if you have DataLabel properties assigned to your ExcelPieChart and then also attempt to assign the DataLabel properties on the ExcelPieChartSerie is does not apply the property to the ExcelPieChartSerie. In order to fix this remove any of the DataLabel properties on the ExcelPieChart and instead add them to the ExcelPieChartSerie as shown below.

private void AddPieChart(ExcelWorksheet worksheet, int firstDataRow, int firstDataColumn, int lastDataRow, int nextColumn, int firstColumn)
        {
            ExcelPieChart pieChart = worksheet.Drawings.AddChart(worksheet.Name.ToString() + " Pie Chart", eChartType.Pie3D) as ExcelPieChart;
            var serie = pieChart.Series.Add(ExcelCellBase.GetAddress(firstDataRow + 3, firstDataColumn, lastDataRow + 3, firstDataColumn),
                                            ExcelCellBase.GetAddress(firstDataRow + 3, firstColumn, lastDataRow + 3, firstColumn));
            pieChart.Legend.Remove();
            pieChart.SetSize(500, 350);
            pieChart.SetPosition(lastDataRow + 5, 0, nextColumn - 1, 0);
            pieChart.Border.Fill.Color = Color.White;
            pieChart.Series.Chart.RoundedCorners = false;

            var pieSerie = (ExcelPieChartSerie)serie;
            pieSerie.DataLabel.ShowCategory = true;
            pieSerie.DataLabel.ShowLeaderLines = true;
            pieSerie.DataLabel.Font.Bold = true;
            pieSerie.DataLabel.Font.Size = 12;
            pieSerie.DataLabel.Position = eLabelPosition.OutEnd;
        }