varwb=newXLWorkbook();varws=wb.Worksheets.Add("Formulas");ws.Cell(1,1).Value="Num1";ws.Cell(1,2).Value="Num2";ws.Cell(1,3).Value="Total";ws.Cell(1,4).Value="cell.FormulaA1";ws.Cell(1,5).Value="cell.FormulaR1C1";ws.Cell(1,6).Value="cell.Value";ws.Cell(1,7).Value="Are Equal?";ws.Cell(2,1).Value=1;ws.Cell(2,2).Value=2;varcellWithFormulaA1=ws.Cell(2,3);// Use A1 notationcellWithFormulaA1.FormulaA1="=A2+$B$2";// The equal sign (=) in a formula is optionalws.Cell(2,4).Value=cellWithFormulaA1.FormulaA1;ws.Cell(2,5).Value=cellWithFormulaA1.FormulaR1C1;ws.Cell(2,6).Value=cellWithFormulaA1.Value;ws.Cell(3,1).Value=1;ws.Cell(3,2).Value=2;varcellWithFormulaR1C1=ws.Cell(3,3);// Use R1C1 notationcellWithFormulaR1C1.FormulaR1C1="RC[-2]+R3C2";// The equal sign (=) in a formula is optionalws.Cell(3,4).Value=cellWithFormulaR1C1.FormulaA1;ws.Cell(3,5).Value=cellWithFormulaR1C1.FormulaR1C1;ws.Cell(3,6).Value=cellWithFormulaR1C1.Value;ws.Cell(4,1).Value="A";ws.Cell(4,2).Value="B";varcellWithStringFormula=ws.Cell(4,3);// Use R1C1 notationcellWithStringFormula.FormulaR1C1="=\"Test\" & RC[-2] &\"R3C2\"";ws.Cell(4,4).Value=cellWithStringFormula.FormulaA1;ws.Cell(4,5).Value=cellWithStringFormula.FormulaR1C1;ws.Cell(4,6).Value=cellWithStringFormula.Value;// Setting the formula of a rangevarrngData=ws.Range(2,1,4,7);rngData.LastColumn().FormulaR1C1="=IF(RC[-3]=RC[-1],\"Yes\",\"No\")";// Using an array formula:// Just put the formula between curly bracesws.Cell("A6").Value="Array Formula: ";ws.Cell("B6").FormulaA1="{A2+A3}";ws.Range(1,1,1,7).Style.Fill.BackgroundColor=XLColor.Cyan;ws.Range(1,1,1,7).Style.Font.Bold=true;ws.Columns().AdjustToContents();// You can also change the reference notation:wb.ReferenceStyle=XLReferenceStyle.R1C1;// And the workbook calculation mode:wb.CalculateMode=XLCalculateMode.Auto;wb.SaveAs("Formulas.xlsx");