The sample demonstrates how to calculate formulas

using System;
using System.IO;
using System.Windows.Forms;
using Spire.Xls;

namespace DataCalculateWithFormulas
{
    class Program
    {
        static void Main(string[] args)
        {
            using (Stream buffer = WriteFormulas())
            {
                //load
                Workbook workbook = new Workbook();
                workbook.LoadFromStream(buffer);

                //calculate formula
                Object b3 = workbook.CaculateFormulaValue("=Sheet1!$B$3");
                Object c3 = workbook.CaculateFormulaValue("=Sheet1!$C$3");
                String formula = "=Sheet1!$B$3 + Sheet1!$C$3";
                Object value = workbook.CaculateFormulaValue(formula);
                String message
                    = String.Format("Sheet1!$B$3 = {0}, Sheet1!$C$3 = {1}, {2} = {3}", b3, c3, formula.Substring(1), value);
                MessageBox.Show(message, "Calculate Formulas");
            }
        }
        private static Stream WriteFormulas()
        {
            //Create Excel files

            Workbook workbook = new Workbook();
            Worksheet sheet = workbook.Worksheets[0];//it's the first sheet of the worksheets

            int currentRow = 1;
            string currentFormula = string.Empty;
            sheet.SetColumnWidth(1, 32);//SetColumnWidth(columnIndex,width);
            sheet.SetColumnWidth(2, 16);
            sheet.SetColumnWidth(3, 16);
            sheet.Range[currentRow++, 1].Value = "Examples of formulas :";
            sheet.Range[++currentRow, 1].Value = "Test data:";

            CellRange range = sheet.Range["A1"];
            range.Style.Font.IsBold = true;
            range.Style.FillPattern = ExcelPatternType.Solid;
            range.Style.KnownColor = ExcelColors.LightGreen1;
            range.Style.Borders[BordersLineType.EdgeBottom].LineStyle = LineStyleType.Medium;

            //test data
            sheet.Range[currentRow, 2].NumberValue = 7.3;
            sheet.Range[currentRow, 3].NumberValue = 5; ;
            sheet.Range[currentRow, 4].NumberValue = 8.2;
            sheet.Range[currentRow, 5].NumberValue = 4;
            sheet.Range[currentRow, 6].NumberValue = 3;
            sheet.Range[currentRow, 7].NumberValue = 11.3;

            MemoryStream buffer = new MemoryStream();
            workbook.SaveToStream(buffer);
            buffer.Position = 0;
            return buffer;
        }
    }
}

Imports System.IO
Imports System.Windows.Forms
Imports Spire.Xls

Module Module1
    Private Function WriteFormulas() As Stream
        Dim workbook As Workbook = New Workbook()
        Dim sheet As Worksheet = workbook.Worksheets(0)

        Dim currentRow As Integer = 1
        Dim currentFormula As String = String.Empty

        sheet.SetColumnWidth(1, 32)
        sheet.SetColumnWidth(2, 16)
        sheet.SetColumnWidth(3, 16)

        currentRow = currentRow + 1
        sheet.Range(currentRow, 1).Value = "Examples of formulas :"
        currentRow = currentRow + 1
        sheet.Range(currentRow, 1).Value = "Test data:"

        Dim range As CellRange = sheet.Range("A1")
        range.Style.Font.IsBold = True
        range.Style.FillPattern = ExcelPatternType.Solid
        range.Style.KnownColor = ExcelColors.LightGreen1
        range.Style.Borders(BordersLineType.EdgeBottom).LineStyle = LineStyleType.Medium

        'test data
        sheet.Range(currentRow, 2).NumberValue = 7.3
        sheet.Range(currentRow, 3).NumberValue = 5

        sheet.Range(currentRow, 4).NumberValue = 8.2
        sheet.Range(currentRow, 5).NumberValue = 4
        sheet.Range(currentRow, 6).NumberValue = 3
        sheet.Range(currentRow, 7).NumberValue = 11.3

        Dim buffer As New MemoryStream()
        workbook.SaveToStream(buffer)
        buffer.Position = 0

        Return buffer
    End Function
    Sub Main()
        Using buffer As Stream = WriteFormulas()
            'load
            Dim workbook As New Workbook()
            workbook.LoadFromStream(buffer)

            'calculate formula
            Dim b3 As Object = workbook.CaculateFormulaValue("=Sheet1!$B$3")
            Dim c3 As Object = workbook.CaculateFormulaValue("=Sheet1!$C$3")
            Dim formula As String = "=Sheet1!$B$3 + Sheet1!$C$3"
            Dim value As Object = workbook.CaculateFormulaValue(formula)
            Dim message As String = _
                String.Format("Sheet1!$B$3 = {0}, Sheet1!$C$3 = {1}, {2} = {3}", b3, c3, formula.Substring(1), value)
            MessageBox.Show(message, "Calculate Formulas")
        End Using
    End Sub
End Module

The sample demonstrates how to export data to datatable with calculating formulas

using System.Data;
using System.IO;
using System.Windows.Forms;

using Spire.Xls;

namespace DataExportWithFormulas
{
    class Program
    {
        static void Main(string[] args)
        {
            DataTable dataTable = null;
            using (Stream buffer = WriteFormulas())
            {
                //load
                Workbook workbook = new Workbook();

                //load the file and import the data
                workbook.LoadFromStream(buffer);  //import the data of the buffer into the excel file;

                //calculate all cells
                workbook.CalculateAllValue();

                //export
                Worksheet sheet = workbook.Worksheets[0];
                dataTable = sheet.ExportDataTable(sheet["A4:B46"], true, true);
            }

            using (Form frm1 = new Form())
            {
                DataGrid dataGrid = new DataGrid();
                dataGrid.CaptionVisible = false;
                dataGrid.ReadOnly = true;
                dataGrid.DataSource = dataTable;
                dataGrid.Dock = DockStyle.Fill;

                frm1.Text = "Data Export with Formulas";
                frm1.Width = 480;
                frm1.Height = 360;
                frm1.StartPosition = FormStartPosition.CenterParent;
                frm1.Controls.Add(dataGrid);
                frm1.ShowDialog();
            }
        }

        private static Stream WriteFormulas()
        {
            //Create Excel files

            Workbook workbook = new Workbook();
            Worksheet sheet = workbook.Worksheets[0];//it's the first sheet of the worksheets

            int currentRow = 1;
            string currentFormula = string.Empty;
            sheet.SetColumnWidth(1, 32);//SetColumnWidth(columnIndex,width);
            sheet.SetColumnWidth(2, 16);
            sheet.SetColumnWidth(3, 16);
            sheet.Range[currentRow++, 1].Value = "Examples of formulas :";
            sheet.Range[++currentRow, 1].Value = "Test data:";

            CellRange range = sheet.Range["A1"];
            range.Style.Font.IsBold = true;
            range.Style.FillPattern = ExcelPatternType.Solid;
            range.Style.KnownColor = ExcelColors.LightGreen1;
            range.Style.Borders[BordersLineType.EdgeBottom].LineStyle = LineStyleType.Medium;

            //test data
            sheet.Range[currentRow, 2].NumberValue = 7.3;
            sheet.Range[currentRow, 3].NumberValue = 5; ;
            sheet.Range[currentRow, 4].NumberValue = 8.2;
            sheet.Range[currentRow, 5].NumberValue = 4;
            sheet.Range[currentRow, 6].NumberValue = 3;
            sheet.Range[currentRow, 7].NumberValue = 11.3;

            sheet.Range[++currentRow, 1].Value = "Formulas"; ;
            sheet.Range[currentRow, 2].Value = "Results";
            range = sheet.Range[currentRow, 1, currentRow, 2];

            //range.Value = "Formulas";
            range.Style.Font.IsBold = true;
            range.Style.KnownColor = ExcelColors.LightGreen1;
            range.Style.FillPattern = ExcelPatternType.Solid;
            range.Style.Borders[BordersLineType.EdgeBottom].LineStyle = LineStyleType.Medium;

            //str.
            currentFormula = "=\"hello\"";
            sheet.Range[++currentRow, 1].Text = "=\"hello\"";
            sheet.Range[currentRow, 2].Formula = currentFormula;
            sheet.Range[currentRow, 3].Formula = "=\"\u4f60\u597d\"";
            
            //int.
            currentFormula = "=300";
            sheet.Range[++currentRow, 1].Text = currentFormula;
            sheet.Range[currentRow, 2].Formula = currentFormula;

            // float                        
            currentFormula = "=3389.639421";
            sheet.Range[++currentRow, 1].Text = currentFormula;
            sheet.Range[currentRow, 2].Formula = currentFormula;

            //bool.
            currentFormula = "=false";
            sheet.Range[++currentRow, 1].Text = currentFormula;
            sheet.Range[currentRow, 2].Formula = currentFormula;

            currentFormula = "=1+2+3+4+5-6-7+8-9";
            sheet.Range[++currentRow, 1].Text = currentFormula;
            sheet.Range[currentRow, 2].Formula = currentFormula;

            currentFormula = "=33*3/4-2+10";
            sheet.Range[++currentRow, 1].Text = currentFormula;
            sheet.Range[currentRow, 2].Formula = currentFormula;


            // sheet reference
            currentFormula = "=Sheet1!$B$3";
            sheet.Range[++currentRow, 1].Text = currentFormula;
            sheet.Range[currentRow, 2].Formula = currentFormula;

            // sheet area reference
            currentFormula = "=AVERAGE(Sheet1!$D$3:G$3)";
            sheet.Range[++currentRow, 1].Text = currentFormula;
            sheet.Range[currentRow, 2].Formula = currentFormula;

            // Functions
            currentFormula = "=Count(3,5,8,10,2,34)";
            sheet.Range[++currentRow, 1].Text = currentFormula;
            sheet.Range[currentRow, 2].Formula = currentFormula;


            currentFormula = "=NOW()";
            sheet.Range[++currentRow, 1].Text = currentFormula;
            sheet.Range[currentRow, 2].Formula = currentFormula;
            sheet.Range[currentRow, 2].Style.NumberFormat = "yyyy-MM-DD";

            currentFormula = "=SECOND(11)";
            sheet.Range[++currentRow, 1].Text = currentFormula;
            sheet.Range[currentRow++, 2].Formula = currentFormula;

            currentFormula = "=MINUTE(12)";
            sheet.Range[currentRow, 1].Text = currentFormula;
            sheet.Range[currentRow++, 2].Formula = currentFormula;

            currentFormula = "=MONTH(9)";
            sheet.Range[currentRow, 1].Text = currentFormula;
            sheet.Range[currentRow++, 2].Formula = currentFormula;

            currentFormula = "=DAY(10)";
            sheet.Range[currentRow, 1].Text = currentFormula;
            sheet.Range[currentRow++, 2].Formula = currentFormula;

            currentFormula = "=TIME(4,5,7)";
            sheet.Range[currentRow, 1].Text = currentFormula;
            sheet.Range[currentRow++, 2].Formula = currentFormula;

            currentFormula = "=DATE(6,4,2)";
            sheet.Range[currentRow, 1].Text = currentFormula;
            sheet.Range[currentRow++, 2].Formula = currentFormula;

            currentFormula = "=RAND()";
            sheet.Range[currentRow, 1].Text = currentFormula;
            sheet.Range[currentRow++, 2].Formula = currentFormula;

            currentFormula = "=HOUR(12)";
            sheet.Range[currentRow, 1].Text = currentFormula;
            sheet.Range[currentRow++, 2].Formula = currentFormula;

            currentFormula = "=MOD(5,3)";
            sheet.Range[currentRow, 1].Text = currentFormula;
            sheet.Range[currentRow++, 2].Formula = currentFormula;

            currentFormula = "=WEEKDAY(3)";
            sheet.Range[currentRow, 1].Text = currentFormula;
            sheet.Range[currentRow++, 2].Formula = currentFormula;

            currentFormula = "=YEAR(23)";
            sheet.Range[currentRow, 1].Text = currentFormula;
            sheet.Range[currentRow++, 2].Formula = currentFormula;

            currentFormula = "=NOT(true)";
            sheet.Range[currentRow, 1].Text = currentFormula;
            sheet.Range[currentRow++, 2].Formula = currentFormula;

            currentFormula = "=OR(true)";
            sheet.Range[currentRow, 1].Text = currentFormula;
            sheet.Range[currentRow++, 2].Formula = currentFormula;

            currentFormula = "=AND(TRUE)";
            sheet.Range[currentRow, 1].Text = currentFormula;
            sheet.Range[currentRow++, 2].Formula = currentFormula;

            currentFormula = "=VALUE(30)";
            sheet.Range[currentRow, 1].Text = currentFormula;
            sheet.Range[currentRow++, 2].Formula = currentFormula;

            currentFormula = "=LEN(\"world\")";
            sheet.Range[currentRow, 1].Text = currentFormula;
            sheet.Range[currentRow++, 2].Formula = currentFormula;

            currentFormula = "=MID(\"world\",4,2)";
            sheet.Range[currentRow, 1].Text = currentFormula;
            sheet.Range[currentRow++, 2].Formula = currentFormula;

            currentFormula = "=ROUND(7,3)";
            sheet.Range[currentRow, 1].Text = currentFormula;
            sheet.Range[currentRow++, 2].Formula = currentFormula;

            currentFormula = "=SIGN(4)";
            sheet.Range[currentRow, 1].Text = currentFormula;
            sheet.Range[currentRow++, 2].Formula = currentFormula;

            currentFormula = "=INT(200)";
            sheet.Range[currentRow, 1].Text = currentFormula;
            sheet.Range[currentRow++, 2].Formula = currentFormula;

            currentFormula = "=ABS(-1.21)";
            sheet.Range[currentRow, 1].Text = currentFormula;
            sheet.Range[currentRow++, 2].Formula = currentFormula;

            currentFormula = "=LN(15)";
            sheet.Range[currentRow, 1].Text = currentFormula;
            sheet.Range[currentRow++, 2].Formula = currentFormula;

            currentFormula = "=EXP(20)";
            sheet.Range[currentRow, 1].Text = currentFormula;
            sheet.Range[currentRow++, 2].Formula = currentFormula;

            currentFormula = "=SQRT(40)";
            sheet.Range[currentRow, 1].Text = currentFormula;
            sheet.Range[currentRow++, 2].Formula = currentFormula;

            currentFormula = "=PI()";
            sheet.Range[currentRow, 1].Text = currentFormula;
            sheet.Range[currentRow++, 2].Formula = currentFormula;

            currentFormula = "=COS(9)";
            sheet.Range[currentRow, 1].Text = currentFormula;
            sheet.Range[currentRow++, 2].Formula = currentFormula;

            currentFormula = "=SIN(45)";
            sheet.Range[currentRow, 1].Text = currentFormula;
            sheet.Range[currentRow++, 2].Formula = currentFormula;

            currentFormula = "=MAX(10,30)";
            sheet.Range[currentRow, 1].Text = currentFormula;
            sheet.Range[currentRow++, 2].Formula = currentFormula;

            currentFormula = "=MIN(5,7)";
            sheet.Range[currentRow, 1].Text = currentFormula;
            sheet.Range[currentRow++, 2].Formula = currentFormula;

            currentFormula = "=AVERAGE(12,45)";
            sheet.Range[currentRow, 1].Text = currentFormula;
            sheet.Range[currentRow++, 2].Formula = currentFormula;

            currentFormula = "=SUM(18,29)";
            sheet.Range[currentRow, 1].Text = currentFormula;
            sheet.Range[currentRow++, 2].Formula = currentFormula;

            currentFormula = "=IF(4,2,2)";
            sheet.Range[currentRow, 1].Text = currentFormula;
            sheet.Range[currentRow++, 2].Formula = currentFormula;

            MemoryStream buffer = new MemoryStream();
            workbook.SaveToStream(buffer);
            buffer.Position = 0;
            return buffer;
        }
    }
}

Imports System.IO
Imports Spire.Xls
Imports System.Windows.Forms

Module Module1

    Private Function WriteFormulas() As Stream
        Dim workbook As Workbook = New Workbook()
        Dim sheet As Worksheet = workbook.Worksheets(0)

        Dim currentRow As Integer = 1
        Dim currentFormula As String = String.Empty

        sheet.SetColumnWidth(1, 32)
        sheet.SetColumnWidth(2, 16)
        sheet.SetColumnWidth(3, 16)

        currentRow = currentRow + 1
        sheet.Range(currentRow, 1).Value = "Examples of formulas :"
        currentRow = currentRow + 1
        sheet.Range(currentRow, 1).Value = "Test data:"

        Dim range As CellRange = sheet.Range("A1")
        range.Style.Font.IsBold = True
        range.Style.FillPattern = ExcelPatternType.Solid
        range.Style.KnownColor = ExcelColors.LightGreen1
        range.Style.Borders(BordersLineType.EdgeBottom).LineStyle = LineStyleType.Medium

        'test data
        sheet.Range(currentRow, 2).NumberValue = 7.3
        sheet.Range(currentRow, 3).NumberValue = 5

        sheet.Range(currentRow, 4).NumberValue = 8.2
        sheet.Range(currentRow, 5).NumberValue = 4
        sheet.Range(currentRow, 6).NumberValue = 3
        sheet.Range(currentRow, 7).NumberValue = 11.3

        currentRow = currentRow + 1
        sheet.Range(currentRow, 1).Value = "Formulas"

        sheet.Range(currentRow, 2).Value = "Results"
        range = sheet.Range(currentRow, 1, currentRow, 2)
        range.Style.Font.IsBold = True
        range.Style.KnownColor = ExcelColors.LightGreen1
        range.Style.FillPattern = ExcelPatternType.Solid
        range.Style.Borders(BordersLineType.EdgeBottom).LineStyle = LineStyleType.Medium
        'str.
        currentFormula = "=""hello"""
        currentRow = currentRow + 1
        sheet.Range(currentRow, 1).Text = "=""hello"""
        sheet.Range(currentRow, 2).Formula = currentFormula
        sheet.Range(currentRow, 3).Formula = "=""" & ChrW(20320) & ChrW(22909) + """"

        'int.
        currentFormula = "=300"
        currentRow = currentRow + 1
        sheet.Range(currentRow, 1).Text = currentFormula
        sheet.Range(currentRow, 2).Formula = currentFormula

        ' float
        currentFormula = "=3389.639421"
        currentRow = currentRow + 1
        sheet.Range(currentRow, 1).Text = currentFormula
        sheet.Range(currentRow, 2).Formula = currentFormula

        'bool.
        currentFormula = "=false"
        currentRow = currentRow + 1
        sheet.Range(currentRow, 1).Text = currentFormula
        sheet.Range(currentRow, 2).Formula = currentFormula

        currentFormula = "=1+2+3+4+5-6-7+8-9"
        currentRow = currentRow + 1
        sheet.Range(currentRow, 1).Text = currentFormula
        sheet.Range(currentRow, 2).Formula = currentFormula

        currentFormula = "=33*3/4-2+10"
        currentRow = currentRow + 1
        sheet.Range(currentRow, 1).Text = currentFormula
        sheet.Range(currentRow, 2).Formula = currentFormula


        ' sheet reference
        currentFormula = "=Sheet1!$B$3"
        currentRow = currentRow + 1
        sheet.Range(currentRow, 1).Text = currentFormula
        sheet.Range(currentRow, 2).Formula = currentFormula

        ' sheet area reference
        currentFormula = "=AVERAGE(Sheet1!$D$3:G$3)"
        currentRow = currentRow + 1
        sheet.Range(currentRow, 1).Text = currentFormula
        sheet.Range(currentRow, 2).Formula = currentFormula

        ' Functions
        currentFormula = "=Count(3,5,8,10,2,34)"
        currentRow = currentRow + 1
        sheet.Range(currentRow, 1).Text = currentFormula
        sheet.Range(currentRow, 2).Formula = currentFormula


        currentFormula = "=NOW()"
        currentRow = currentRow + 1
        sheet.Range(currentRow, 1).Text = currentFormula
        sheet.Range(currentRow, 2).Formula = currentFormula
        sheet.Range(currentRow, 2).Style.NumberFormat = "yyyy-MM-DD"


        currentFormula = "=SECOND(11)"
        currentRow = currentRow + 1
        sheet.Range(currentRow, 1).Text = currentFormula
        sheet.Range(currentRow, 2).Formula = currentFormula

        currentFormula = "=MINUTE(12)"
        currentRow = currentRow + 1
        sheet.Range(currentRow, 1).Text = currentFormula
        sheet.Range(currentRow, 2).Formula = currentFormula

        currentFormula = "=MONTH(9)"
        currentRow = currentRow + 1
        sheet.Range(currentRow, 1).Text = currentFormula
        sheet.Range(currentRow, 2).Formula = currentFormula

        currentFormula = "=DAY(10)"
        currentRow = currentRow + 1
        sheet.Range(currentRow, 1).Text = currentFormula
        sheet.Range(currentRow, 2).Formula = currentFormula

        currentFormula = "=TIME(4,5,7)"
        currentRow = currentRow + 1
        sheet.Range(currentRow, 1).Text = currentFormula
        sheet.Range(currentRow, 2).Formula = currentFormula

        currentFormula = "=DATE(6,4,2)"
        currentRow = currentRow + 1
        sheet.Range(currentRow, 1).Text = currentFormula
        sheet.Range(currentRow, 2).Formula = currentFormula

        currentFormula = "=RAND()"
        currentRow = currentRow + 1
        sheet.Range(currentRow, 1).Text = currentFormula
        sheet.Range(currentRow, 2).Formula = currentFormula

        currentFormula = "=HOUR(12)"
        currentRow = currentRow + 1
        sheet.Range(currentRow, 1).Text = currentFormula
        sheet.Range(currentRow, 2).Formula = currentFormula

        currentFormula = "=MOD(5,3)"
        currentRow = currentRow + 1
        sheet.Range(currentRow, 1).Text = currentFormula
        sheet.Range(currentRow, 2).Formula = currentFormula

        currentFormula = "=WEEKDAY(3)"
        currentRow = currentRow + 1
        sheet.Range(currentRow, 1).Text = currentFormula
        sheet.Range(currentRow, 2).Formula = currentFormula

        currentFormula = "=YEAR(23)"
        currentRow = currentRow + 1
        sheet.Range(currentRow, 1).Text = currentFormula
        sheet.Range(currentRow, 2).Formula = currentFormula

        currentFormula = "=NOT(true)"
        currentRow = currentRow + 1
        sheet.Range(currentRow, 1).Text = currentFormula
        sheet.Range(currentRow, 2).Formula = currentFormula

        currentFormula = "=OR(true)"
        currentRow = currentRow + 1
        sheet.Range(currentRow, 1).Text = currentFormula
        sheet.Range(currentRow, 2).Formula = currentFormula

        currentFormula = "=AND(TRUE)"
        currentRow = currentRow + 1
        sheet.Range(currentRow, 1).Text = currentFormula
        sheet.Range(currentRow, 2).Formula = currentFormula

        currentFormula = "=VALUE(30)"
        currentRow = currentRow + 1
        sheet.Range(currentRow, 1).Text = currentFormula
        sheet.Range(currentRow, 2).Formula = currentFormula

        currentFormula = "=LEN(""world"")"
        currentRow = currentRow + 1
        sheet.Range(currentRow, 1).Text = currentFormula
        sheet.Range(currentRow, 2).Formula = currentFormula

        currentFormula = "=MID(""world"",4,2)"
        currentRow = currentRow + 1
        sheet.Range(currentRow, 1).Text = currentFormula
        sheet.Range(currentRow, 2).Formula = currentFormula

        currentFormula = "=ROUND(7,3)"
        currentRow = currentRow + 1
        sheet.Range(currentRow, 1).Text = currentFormula
        sheet.Range(currentRow, 2).Formula = currentFormula

        currentFormula = "=SIGN(4)"
        currentRow = currentRow + 1
        sheet.Range(currentRow, 1).Text = currentFormula
        sheet.Range(currentRow, 2).Formula = currentFormula

        currentFormula = "=INT(200)"
        currentRow = currentRow + 1
        sheet.Range(currentRow, 1).Text = currentFormula
        sheet.Range(currentRow, 2).Formula = currentFormula

        currentFormula = "=ABS(-1.21)"
        currentRow = currentRow + 1
        sheet.Range(currentRow, 1).Text = currentFormula
        sheet.Range(currentRow, 2).Formula = currentFormula

        currentFormula = "=LN(15)"
        currentRow = currentRow + 1
        sheet.Range(currentRow, 1).Text = currentFormula
        sheet.Range(currentRow, 2).Formula = currentFormula

        currentFormula = "=EXP(20)"
        currentRow = currentRow + 1
        sheet.Range(currentRow, 1).Text = currentFormula
        sheet.Range(currentRow, 2).Formula = currentFormula

        currentFormula = "=SQRT(40)"
        currentRow = currentRow + 1
        sheet.Range(currentRow, 1).Text = currentFormula
        sheet.Range(currentRow, 2).Formula = currentFormula

        currentFormula = "=PI()"
        currentRow = currentRow + 1
        sheet.Range(currentRow, 1).Text = currentFormula
        sheet.Range(currentRow, 2).Formula = currentFormula

        currentFormula = "=COS(9)"
        currentRow = currentRow + 1
        sheet.Range(currentRow, 1).Text = currentFormula
        sheet.Range(currentRow, 2).Formula = currentFormula

        currentFormula = "=SIN(45)"
        currentRow = currentRow + 1
        sheet.Range(currentRow, 1).Text = currentFormula
        sheet.Range(currentRow, 2).Formula = currentFormula

        currentFormula = "=MAX(10,30)"
        currentRow = currentRow + 1
        sheet.Range(currentRow, 1).Text = currentFormula
        sheet.Range(currentRow, 2).Formula = currentFormula

        currentFormula = "=MIN(5,7)"
        currentRow = currentRow + 1
        sheet.Range(currentRow, 1).Text = currentFormula
        sheet.Range(currentRow, 2).Formula = currentFormula

        currentFormula = "=AVERAGE(12,45)"
        currentRow = currentRow + 1
        sheet.Range(currentRow, 1).Text = currentFormula
        sheet.Range(currentRow, 2).Formula = currentFormula

        currentFormula = "=SUM(18,29)"
        currentRow = currentRow + 1
        sheet.Range(currentRow, 1).Text = currentFormula
        sheet.Range(currentRow, 2).Formula = currentFormula

        currentFormula = "=IF(4,2,2)"
        currentRow = currentRow + 1
        sheet.Range(currentRow, 1).Text = currentFormula
        sheet.Range(currentRow, 2).Formula = currentFormula

        Dim buffer As New MemoryStream()
        workbook.SaveToStream(buffer)
        buffer.Position = 0

        Return buffer
    End Function
    Sub Main()
        Dim dataTable As DataTable
        Using buffer As Stream = WriteFormulas()
            'load
            Dim workbook As New Workbook()
            workbook.LoadFromStream(buffer)

            'calculate all cells
            workbook.CalculateAllValue()

            'export
            Dim sheet As Worksheet = workbook.Worksheets(0)
            dataTable = sheet.ExportDataTable(sheet("A4:B46"), True, True)
        End Using

        Using frm1 As New Form()
            Dim dataGrid As New DataGrid()
            dataGrid.CaptionVisible = False
            dataGrid.ReadOnly = True
            dataGrid.DataSource = dataTable
            dataGrid.Dock = DockStyle.Fill

            frm1.Text = "Data Export with Formulas"
            frm1.Width = 480
            frm1.Height = 360
            frm1.StartPosition = FormStartPosition.CenterParent
            frm1.Controls.Add(dataGrid)
            frm1.ShowDialog()
        End Using
    End Sub
End Module

The sample demonstrates how to insert SparkLine into an excel workbook.

using Spire.Xls;
using System.Drawing;

namespace SparkLine
{
    class Program
    {
        static void Main(string[] args)
        {
            Workbook workbook = new Workbook();
            workbook.Version = ExcelVersion.Version2010;
            workbook.CreateEmptySheets(1);

            Worksheet sheet = workbook.Worksheets[0];

            //Country
            sheet.Range["A1"].Value = "Country";
            sheet.Range["A2"].Value = "Cuba";
            sheet.Range["A3"].Value = "Mexico";
            sheet.Range["A4"].Value = "France";
            sheet.Range["A5"].Value = "German";

            //Jun
            sheet.Range["B1"].Value = "Jun";
            sheet.Range["B2"].NumberValue = 0.23;
            sheet.Range["B3"].NumberValue = 0.37;
            sheet.Range["B4"].NumberValue = 0.15;
            sheet.Range["B5"].NumberValue = 0.25;

            //Jul
            sheet.Range["C1"].Value = "Jul";
            sheet.Range["C2"].NumberValue = 0.1;
            sheet.Range["C3"].NumberValue = 0.35;
            sheet.Range["C4"].NumberValue = 0.22;
            sheet.Range["C5"].NumberValue = 0.33;


            //Aug
            sheet.Range["D1"].Value = "Aug";
            sheet.Range["D2"].NumberValue = 0.14;
            sheet.Range["D3"].NumberValue = 0.36;
            sheet.Range["D4"].NumberValue = 0.25;
            sheet.Range["D5"].NumberValue = 0.25;


            //Sep
            sheet.Range["E1"].Value = "Sep";
            sheet.Range["E2"].NumberValue = 0.17;
            sheet.Range["E3"].NumberValue = 0.28;
            sheet.Range["E4"].NumberValue = 0.39;
            sheet.Range["E5"].NumberValue = 0.32;

            //Style
            sheet.Range["A1:E1"].Style.Font.IsBold = true;
            sheet.Range["A2:E2"].Style.KnownColor = ExcelColors.LightYellow;
            sheet.Range["A3:E3"].Style.KnownColor = ExcelColors.LightGreen1;
            sheet.Range["A4:E4"].Style.KnownColor = ExcelColors.LightOrange;
            sheet.Range["A5:E5"].Style.KnownColor = ExcelColors.LightTurquoise;

            //Border
            sheet.Range["A1:E5"].Style.Borders[BordersLineType.EdgeTop].Color = Color.FromArgb(0, 0, 128);
            sheet.Range["A1:E5"].Style.Borders[BordersLineType.EdgeTop].LineStyle = LineStyleType.Thin;
            sheet.Range["A1:E5"].Style.Borders[BordersLineType.EdgeBottom].Color = Color.FromArgb(0, 0, 128);
            sheet.Range["A1:E5"].Style.Borders[BordersLineType.EdgeBottom].LineStyle = LineStyleType.Thin;
            sheet.Range["A1:E5"].Style.Borders[BordersLineType.EdgeLeft].Color = Color.FromArgb(0, 0, 128);
            sheet.Range["A1:E5"].Style.Borders[BordersLineType.EdgeLeft].LineStyle = LineStyleType.Thin;
            sheet.Range["A1:E5"].Style.Borders[BordersLineType.EdgeRight].Color = Color.FromArgb(0, 0, 128);
            sheet.Range["A1:E5"].Style.Borders[BordersLineType.EdgeRight].LineStyle = LineStyleType.Thin;

            sheet.Range["B2:D5"].Style.NumberFormatIndex = 9;

            SparklineGroup sparklineGroup
                = sheet.SparklineGroups.AddGroup(SparklineType.Line);
            SparklineCollection sparklines = sparklineGroup.Add();
            sparklines.Add(sheet["B2:E2"], sheet["F2"]);
            sparklines.Add(sheet["B3:E3"], sheet["F3"]);
            sparklines.Add(sheet["B4:E4"], sheet["F4"]);
            sparklines.Add(sheet["B5:E5"], sheet["F5"]);

            workbook.SaveToFile("Sample.xlsx");
            System.Diagnostics.Process.Start(workbook.FileName);

        }
    }
}

Imports Spire.Xls
Imports System.Drawing
Module Module1
    Sub Main()
        Dim workbook As New Workbook()
        workbook.Version = ExcelVersion.Version2010
        workbook.CreateEmptySheets(1)

        Dim sheet As Worksheet = workbook.Worksheets(0)

        'Country
        sheet.Range("A1").Value = "Country"
        sheet.Range("A2").Value = "Cuba"
        sheet.Range("A3").Value = "Mexico"
        sheet.Range("A4").Value = "France"
        sheet.Range("A5").Value = "German"

        'Jun
        sheet.Range("B1").Value = "Jun"
        sheet.Range("B2").NumberValue = 0.23
        sheet.Range("B3").NumberValue = 0.37
        sheet.Range("B4").NumberValue = 0.15
        sheet.Range("B5").NumberValue = 0.25

        'Jul
        sheet.Range("C1").Value = "Jul"
        sheet.Range("C2").NumberValue = 0.1
        sheet.Range("C3").NumberValue = 0.35
        sheet.Range("C4").NumberValue = 0.22
        sheet.Range("C5").NumberValue = 0.33


        'Aug
        sheet.Range("D1").Value = "Aug"
        sheet.Range("D2").NumberValue = 0.14
        sheet.Range("D3").NumberValue = 0.36
        sheet.Range("D4").NumberValue = 0.25
        sheet.Range("D5").NumberValue = 0.25


        'Sep
        sheet.Range("E1").Value = "Sep"
        sheet.Range("E2").NumberValue = 0.17
        sheet.Range("E3").NumberValue = 0.28
        sheet.Range("E4").NumberValue = 0.39
        sheet.Range("E5").NumberValue = 0.32

        'Style
        sheet.Range("A1:E1").Style.Font.IsBold = True
        sheet.Range("A2:E2").Style.KnownColor = ExcelColors.LightYellow
        sheet.Range("A3:E3").Style.KnownColor = ExcelColors.LightGreen1
        sheet.Range("A4:E4").Style.KnownColor = ExcelColors.LightOrange
        sheet.Range("A5:E5").Style.KnownColor = ExcelColors.LightTurquoise

        'Border
        sheet.Range("A1:E5").Style.Borders(BordersLineType.EdgeTop).Color = Color.FromArgb(0, 0, 128)
        sheet.Range("A1:E5").Style.Borders(BordersLineType.EdgeTop).LineStyle = LineStyleType.Thin
        sheet.Range("A1:E5").Style.Borders(BordersLineType.EdgeBottom).Color = Color.FromArgb(0, 0, 128)
        sheet.Range("A1:E5").Style.Borders(BordersLineType.EdgeBottom).LineStyle = LineStyleType.Thin
        sheet.Range("A1:E5").Style.Borders(BordersLineType.EdgeLeft).Color = Color.FromArgb(0, 0, 128)
        sheet.Range("A1:E5").Style.Borders(BordersLineType.EdgeLeft).LineStyle = LineStyleType.Thin
        sheet.Range("A1:E5").Style.Borders(BordersLineType.EdgeRight).Color = Color.FromArgb(0, 0, 128)
        sheet.Range("A1:E5").Style.Borders(BordersLineType.EdgeRight).LineStyle = LineStyleType.Thin

        sheet.Range("B2:D5").Style.NumberFormatIndex = 9

        Dim sparklineGroup As SparklineGroup = sheet.SparklineGroups.AddGroup(SparklineType.Line)
        Dim sparklines As SparklineCollection = sparklineGroup.Add()
        sparklines.Add(sheet("B2:E2"), sheet("F2"))
        sparklines.Add(sheet("B3:E3"), sheet("F3"))
        sparklines.Add(sheet("B4:E4"), sheet("F4"))
        sparklines.Add(sheet("B5:E5"), sheet("F5"))

        workbook.SaveToFile("Sample.xlsx")
        System.Diagnostics.Process.Start(workbook.FileName)

    End Sub
End Module