nullreferenceexception was unhandled by user code asp.net

protected void rgDesignation_ItemCommand(object source, GridCommandEventArgs e)
  {
      if (e.CommandName == "InitInsert")
      {
          for (int k = 0; k < rgDesignation.Items.Count; k++)
          {
              if (rgDesignation.Items[k].Edit)
              {
                  e.Canceled = true;
                  return;
              }
          }
      }
      if (e.CommandName == "Edit")
      {
          if (rgDesignation.MasterTableView.IsItemInserted)
          {
              e.Canceled = true;
              return;
          }
          GridEditableItem editItem = (GridEditableItem)e.Item;
          RadTextBox txDesignation = (RadTextBox)editItem.FindControl("txDesignation");

          RadioButton rbYes = (RadioButton)editItem.FindControl("rbYes");
          RadioButton rbNo = (RadioButton)editItem.FindControl("rbNo");
          RadioButton rbUser = (RadioButton)editItem.FindControl("rbUser");
          int DesgID = (int)e.Item.OwnerTableView.DataKeyValues[e.Item.ItemIndex]["DesgID"];
          DataView dv;
          DataSet ds = new DataSet();
          ds = DataAccessLayer.BindDataQuery("select Estatus1 from tblDesignations where DesgID='" + DesgID + "'");
          dv = ds.Tables[0].DefaultView;
          int Name;
          // args.IsValid = true;

          //foreach (DataRowView datarow in dv)
          //{
              int a = 1, b = 2, c = 3;
              Name = Convert.ToInt32(ds.Tables[0].Rows[0]["Estatus1"]);
              if (Name == a)
              {
                  rbYes.Checked = true;
                  rbNo.Checked = false;
                  rbUser.Checked = false;
              }
              else if (Name==b)
              {
                  rbNo.Checked = true;
                  rbYes.Checked = false;
                  rbUser.Checked = false;
              }
              else
              {
                  rbUser.Checked = true;
                  rbNo.Checked = false;
                  rbYes.Checked = false;
              }

          //}
      }
  }