public void clear()
{
foreach (Row r in rows)
{
OnRowDeleted(r);
}
rows.Clear();
// this.FormatRanges.Clear ();
ParseQueue.Clear();
KeywordQueue.Clear();
UndoBuffer.Clear();
UndoStep = 0;
// this.Add ("");
// ResetVisibleRows();
// this.OnChange ();
}