private void cboIssuedTo_SelectedValueChanged(object sender, EventArgs e)
 {
     if (cboIssuedTo.SelectedValue != null)
     {
         DataTable dtItem = new DataTable();
         Items itm = new Items();
         int duId = Convert.ToInt32(cboIssuedTo.SelectedValue);
         dtItem = itm.GetItemsByDU(duId);
         PopulateItemListByDU(dtItem);
     }
 }