Table tbl = new Table();
TableRowGroup trg = new TableRowGroup();

tbl.RowGroups.Add(trg);

// Add rows to a TableRowGroup collection.
int rowsToAdd = 4; 
for (int x = 0; x < rowsToAdd; x++)
    trg.Rows.Add(new TableRow());

// Insert a new first row (at the zero-index position).
trg.Rows.Insert(0, new TableRow());

// Manipulate rows...

// Set the background on the first row.
trg.Rows[0].Background = Brushes.CornflowerBlue;
// Set the font size on the second row.
trg.Rows[1].FontSize = 24;
// Set a tooltip for the third row.
trg.Rows[2].ToolTip = "This row's tooltip";

// Adding cells to a row...
{
    int cellsToAdd = 10;
    for (int x = 0; x < cellsToAdd; x++)
        trg.Rows[0].Cells.Add(new TableCell(new Paragraph(new Run("Cell " + (x + 1)))));
}

// Count rows.
int rows = trg.Rows.Count;

// Remove 1st row by reference.
trg.Rows.Remove(trg.Rows[0]);

// Remove all rows...
trg.Rows.Clear();