public void WaterfallChart()
  {
      // Initialize workbook
      Workbook workbook = new Workbook();
      // Fetch default worksheet 
      IWorksheet worksheet = workbook.Worksheets[0];

      // Prepare data for chart
      worksheet.Range["A1:B8"].Value = new object[,]
{
     {"Starting Amt", 130},
     {"Measurement 1", 25},
     {"Measurement 2", -75},
     {"Subtotal", 80},
     {"Measurement 3", 45},
     {"Measurement 4", -65},
     {"Measurement 5", 80},
     {"Total", 140}
};
      worksheet.Range["A:A"].Columns.AutoFit();

      // Add Waterfall Chart
      IShape waterfallChartShape = worksheet.Shapes.AddChart(ChartType.Waterfall, 300, 20, 300, 250);
      waterfallChartShape.Chart.SeriesCollection.Add(worksheet.Range["A1:B8"]);

      //Set subtotal & total points
      IPoints points = waterfallChartShape.Chart.SeriesCollection[0].Points;
      points[3].IsTotal = true;
      points[7].IsTotal = true;

      //Connector lines are not shown
      ISeries series = waterfallChartShape.Chart.SeriesCollection[0];
      series.ShowConnectorLines = false;

      // Configure Chart Title 
      waterfallChartShape.Chart.ChartTitle.Text = "Waterfall Chart";

      // Saving workbook to Xlsx
      workbook.Save(@"30-WaterfallChart.xlsx", SaveFileFormat.Xlsx);
  }