Sets or returns the 0-based number of the first column within the rectangular area of cells.

 public int FirstColumn{ get; }
Public ReadOnly Property FirstColumn() As Integer

//--- Get FirstColumn
int firstCol = a.FirstColumn;

//--- Set FirstColumn
a.FirstColumn = 5;

'--- Get FirstColumn
Dim firstCol As Integer = a.FirstColumn

'--- Set FirstColumn
a.FirstColumn = 5