FormView内DropDownList選択時のイベント

function mitameHenkou(s, n) {

   var os = event.srcElement;

   

   var tr = os;

   while (tr.tagName.toLowerCase() != "tr") tr = tr.parentNode;

   var td = tr.childNodes[n];

   var chs = td.getElementsByTagName("select");



   if (!!chs) {

      if (os.selectedIndex == s) {

         chs[0].disabled = false;

      }

      else {

        chs[0].disabled = true;

      }

   }

}

Protected Sub DropDownList1_SelectedIndexChanged(...)
  Dim drop2 As DropDownList = _
   CType(FormView1.Row.FindControl("DropDownList2"), DropDownList)
  drop2.Enabled = False
End Sub

<asp:FormView ID="FormView1" runat="server" DataKeyNames="CategoryID" 
  DataSourceID="SqlDataSource1" AllowPaging="True">
  <ItemTemplate>
    DropDownList1:
    <asp:DropDownList ID="DropDownList1" runat="server" 
      AutoPostBack="true" 
      OnSelectedIndexChanged="DropDownList1_SelectedIndexChanged">
      <asp:ListItem>item1</asp:ListItem>
      <asp:ListItem>item2</asp:ListItem>
      <asp:ListItem>item3</asp:ListItem>
    </asp:DropDownList>
    <br />
    DropDownList2:
    <asp:DropDownList ID="DropDownList2" runat="server" 
      AutoPostBack="true" 
      OnSelectedIndexChanged="DropDownList2_SelectedIndexChanged">
      <asp:ListItem>item A</asp:ListItem>
      <asp:ListItem>item B</asp:ListItem>
      <asp:ListItem>item C</asp:ListItem>
    </asp:DropDownList>          
  </ItemTemplate>
</asp:FormView>