public class Worksheet : WorkbookElement 

using( var doc = Workbook.Load( "test.xlsx") ) // Loads an existing Workbook named “test.xlsx”.
  {
    var worksheet = doc.Worksheets[ 1 ]; // Gets the second worksheet. 
    worksheet.Cells[ “A2” ].Value = 12; // Sets a value in “A2”.
    worksheet.Columns[ 1 ].Cells[ 0 ].Formula = “=SUM(A1:A2)”; // Sets a formula in “B1”.
    worksheet.Rows[ 3 ].Cells[ 3 ].Value = 40d; // Sets “D4” Value.
    worksheet.Name = “Years 2021”; // Sets a name for the Worksheet.
    worksheet.SheetView.ActiveCellAddress = “C2”; // Sets the cell with focus.
    worksheet.TabColor = Color.FromArgb( 0, 128, 0 ); // Sets the Tab color.

    worksheet.CalculateFormulas(); // Calculate the Value of “B1”, which contains a formula.
    doc.Save(); 
  }