Calculating Formulas

//Instantiating a Workbook object
Workbook workbook = new Workbook();

//Adding a new worksheet to the Excel object
int sheetIndex = workbook.Worksheets.Add();

//Obtaining the reference of the newly added worksheet by passing its sheet index
Worksheet worksheet = workbook.Worksheets[sheetIndex];

//Adding a value to "A1" cell
worksheet.Cells["A1"].PutValue(1);

//Adding a value to "A2" cell
worksheet.Cells["A2"].PutValue(2);

//Adding a value to "A3" cell
worksheet.Cells["A3"].PutValue(3);

//Adding a SUM formula to "A4" cell
worksheet.Cells["A4"].Formula = "=SUM(A1:A3)";

//Calculating the results of formulas
workbook.CalculateFormula();

//Get the calculated value of the cell
string value = worksheet.Cells["A4"].Value.ToString();

//Saving the Excel file
workbook.Save("D:\\test.xls");
 

'Instantiating a Workbook object
Dim Workbook As Workbook = New Workbook()

'Adding a new worksheet to the Excel object
Dim sheetIndex As Integer = Workbook.Worksheets.Add()

'Obtaining the reference of the newly added worksheet by passing its sheet index
Dim worksheet As Worksheet = Workbook.Worksheets(sheetIndex)

'Adding a value to "A1" cell
worksheet.Cells("A1").PutValue(1)

'Adding a value to "A2" cell
worksheet.Cells("A2").PutValue(2)

'Adding a value to "A3" cell
worksheet.Cells("A3").PutValue(3)

'Adding a SUM formula to "A4" cell
worksheet.Cells("A4").Formula = "=SUM(A1:A3)"

'Calculating the results of formulas
Workbook.CalculateFormula()

'Get the calculated value of the cell
Dim value As String = worksheet.Cells("A4").Value.ToString()

'Saving the Excel file
Workbook.Save("D:\test.xls", FileFormatType.Default)