请问GridView合并相同单元格的方法

protected void GridView1_PreRender(object sender, EventArgs e)
{
GridDecorator.MergeRows(GridView1);

}
public class GridDecorator
{
public static void MergeRows(GridView GridView1)
{
for (int rowIndex = GridView1.Rows.Count -2; rowIndex >= 0; rowIndex--)
{
GridViewRow row = GridView1.Rows[rowIndex];

GridViewRow previousRow = GridView1.Rows[rowIndex+1];

for (int i = 0; i < row.Cells.Count; i++)
{
if (row.Cells[i].Text == previousRow.Cells[i].Text)
{
row.Cells[i].RowSpan = previousRow.Cells[i].RowSpan < 1 ? 2 : previousRow.Cells[i].RowSpan+1;

previousRow.Cells[i].Visible =false;
}
}
}<