1 DataTable dt = (DataTable)gridView1.GridControl.DataSource;
2 DataRow[] drr = dt.Select(gridView1.RowFilter);
3 foreach (DataRow dr in drr)
4 {
5        dr["SelectFlag"] = "1";
6 }
7 gridView1.GridControl.DataSource = dt;
8 gridView1.GridControl.Show();