in gridview how to add new row using asp.net

GridViewRow rw = new GridViewRow(-1, -1, DataControlRowType.DataRow, DataControlRowState.Normal);
           TableCell rowCell;

           int colCount = GridView1.Columns.Count;
           //if your not providing columns at design time in .aspx file
           //then you need provide value for colCount manullay
           //like below commented line
           //int colCount = 3;


           for (int i = 0; i < colCount; i++)
           {
               rowCell = new TableCell();
               rowCell.Text = "celltext";
               rw.Cells.Add(rowCell);
           }
           GridView1.Controls[0].Controls.Add(rw);