Update the value in db

Question

protected void Vote_Click(object sender, EventArgs e) {
 SqlConnection sql = new SqlConnection(conf);
 try {
  foreach(GridViewRow row in voterslist.Rows) {
   CheckBox chk = (CheckBox) row.FindControl("votepoint");
   Label lblCount = (Label) row.FindControl("vote_lbl");
   if (chk.Checked) {
    String Sid = lblCount.Text;
    String nqry = "what command should i enter here? I want to increase the count of the data that i checked in checkbox after the button clicked ";
    SqlCommand cmd = new SqlCommand(nqry, sql);
    int i = cmd.ExecuteNonQuery();
   }
  }
 }
 sql.Open();
}