public int Add(Cell cell)
{
if (cell == null)
{
throw new System.ArgumentNullException("Cell is null");
}
int index = this.List.Add(cell);
this.OnCellAdded(new RowEventArgs(this.owner, cell, index, index));
for (int i = 1; i < cell.ColSpan; i++)
{
this.Add(new Cell(string.Empty));
}
return index;
}