Stopwatch sw = new Stopwatch();
sw.Start();
IWorkbookFormatProvider formatProvider = new Telerik.Windows.Documents.Spreadsheet.FormatProviders.OpenXml.Xlsx.XlsxFormatProvider();
Workbook workbook = new Workbook();
Worksheet worksheet = workbook.Worksheets.Add();
Worksheet worksheet2 = workbook.Worksheets.Add();
worksheet2.Name ="Days";
List<string> weekdays = new List<string>() { "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday", "Sunday"};
for (int i = 0; i < 7; i++)
{
    worksheet2.Cells[0, i].SetValue(weekdays[i]);
}

for (int i = 0; i < 200; i++)
{
    for (int j = 0; j < 10; j++)
    {

        CellIndex cellIndex = new CellIndex(i, j);
        CellSelection selection = worksheet.Cells[cellIndex];
        selection.SetValue("Wednesday");

        var context = new ListDataValidationRuleContext(worksheet, cellIndex)
        {
            InputMessageTitle = "InputMessageTitle",
            InputMessageContent = "InputMessageTitle"
        };

        context.ErrorStyle = ErrorStyle.Stop;
        context.ErrorAlertTitle = "ErrorAlertTitle";
        context.ErrorAlertContent = "ErrorAlertContent";
        context.InCellDropdown = true;
        context.Argument1 = "=Days!A0:A6"; //"Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, Sunday";
        ListDataValidationRule rule = new(context);
        worksheet.Cells[cellIndex].SetDataValidationRule(rule);
    }
}

string outputFile = @"..\..\..\output.xlsx";
File.Delete(outputFile);

using (Stream output = new FileStream(outputFile, FileMode.Create))
{

    formatProvider.Export(workbook, output);
}
sw.Stop();
Debug.WriteLine("Export " + sw.ElapsedMilliseconds);

<?xml version="1.0" encoding="utf-8"?>
<workbook xmlns:r="http://schemas.openxmlformats.org/officeDocument/2006/relationships" xmlns="http://schemas.openxmlformats.org/spreadsheetml/2006/main">
	<sheets>
		<sheet sheetId="1" name="Sheet1" state="visible" r:id="rId1" />
	</sheets>
	<definedNames>
		<definedName name="Print_Titles" localSheetId="0" hidden="false">Sheet1!$A$1:$IV$3</definedName>
		<definedName name="_xlnm.Print_Area" localSheetId="0" hidden="false">Sheet1!$A:$G</definedName>
		<definedName name="_xlnm.Print_Titles" localSheetId="0" hidden="false">Sheet1!$1:$3</definedName>
	</definedNames>
</workbook>

            Workbook workbook = new Workbook();
            Worksheet graphWorksheet = workbook.Worksheets.Add();
            FloatingChartShape chartShape = new FloatingChartShape(graphWorksheet,
                                         new CellIndex(0, 0),
                                         new CellRange(0, 0, 0, 0), ChartType.Column)
            {
                Width = 500,
                Height = 500,
            };

            graphWorksheet.Charts.Add(chartShape);
            DocumentChart chart = new DocumentChart();
            BarSeriesGroup barSeriesGroup = new BarSeriesGroup();
            barSeriesGroup.BarDirection = BarDirection.Column;
            StringChartData barCategoryData = new StringChartData(new List<string>() { "1.1", "1.2", "1.3", "1.4", "2.1", "3.1", "4.1", "4.2", "4.3" });
            IEnumerable<double> percentEvidentList = new List<double>() { Math.Round((double)0.9914 * 100, 4) , Math.Round((double)0.7719 * 100, 4), Math.Round((double)1 * 100, 4)   };
            NumericChartData barValues = new NumericChartData(percentEvidentList);
            BarSeries series = new BarSeries();
            series.Categories = barCategoryData;
            series.Values = barValues;
            ThemableColor themableColor = ThemableColor.FromArgb(255, 125, 0, 125);

            series.Fill = new SolidFill(themableColor);
            series.Title = new TextTitle("FY 20");
            barSeriesGroup.Series.Add(series);
            chart.SeriesGroups.Add(barSeriesGroup);
            ValueAxis valueAxis = new ValueAxis();
            valueAxis.Min = 0;
            valueAxis.Max = 100;
            valueAxis.NumberFormat = "0%";
            CategoryAxis categoryAxis = new CategoryAxis(); 
            chart.PrimaryAxes = new AxisGroup(categoryAxis, valueAxis);

            chart.Legend = new Legend();
            chart.Legend.Position = LegendPosition.Left;

            chartShape.Chart = chart;
            valueAxis.NumberFormat = "0%";
            string outputFilePath = "SampleFile.xlsx";
            File.Delete(outputFilePath);
            IWorkbookFormatProvider formatProvider = new Telerik.Windows.Documents.Spreadsheet.FormatProviders.OpenXml.Xlsx.XlsxFormatProvider();

            using (Stream output = new FileStream(outputFilePath, FileMode.Create))
            {
                formatProvider.Export(workbook, output, TimeSpan.FromSeconds(10));
            }
            Process.Start(new ProcessStartInfo() { FileName = outputFilePath, UseShellExecute = true });