Custom Formula in Windows Forms Spreadsheet

23 Jul 20261 minute to read

Spreadsheet allows you to add custom formulas into its function library by using the AddFunction method of FormulaEngine.

C#

spreadsheet.WorkbookLoaded += spreadsheet_WorkbookLoaded;

void spreadsheet_WorkbookLoaded(object sender, WorkbookLoadedEventArgs args)
{

  // Iterate over every grid in the loaded workbook and register the custom formula on each one.
  foreach (var grid in args.GridCollection)
    AddCustomFormula(grid); 

  //Computing the formula at runtime
   var range = spreadsheet.ActiveSheet.Range["B2"];
   spreadsheet.ActiveGrid.SetCellValue(range,"=FindLength(Sample)");

}

private void AddCustomFormula(SpreadsheetGrid grid)
{

  // Add a formula named FindLength to the library.
   grid.FormulaEngine.AddFunction("FindLength", new FormulaEngine.LibraryFunction(ComputeLength));      
}    

// Custom formula implementation.
    
public string ComputeLength(string range)
{

  // Used to calculate the length of the string.
    return range.Length.ToString();
}