Sets or returns a cell formula. If no formula is associated with the cell, the property returns an empty string.

 public System.String Formula{ get; set; }
Public Property Formula() As String

          //--- Get CellFormula
          string cf = cellA1.Formula;

          //--- Set CellFormula
          cellA1.Formula = "=SUM(A1:A2)";
        

          '--- Get CellFormula
          Dim cf As string = cellA1.Formula

          '--- Set CellFormula
          oCell.Formula = "=SUM(A1:A2)"