更新面板不工作，不知道爲什麼

Question

我想關閉下拉PhoneHelp如果在第一個下拉框中選擇手機，但它似乎並沒有工作。下面是代碼：

.NET

 <asp:DropDownList ID="ddlHowRec" runat="server"> 
      <asp:ListItem Value="" Text="Choose an option"></asp:ListItem> 
      <asp:ListItem Value="mail" Text="Mail"></asp:ListItem> 
      <asp:ListItem Value="e-mail" Text="E-mail"></asp:ListItem> 
      <asp:ListItem Value="phone" Text="Call back"></asp:ListItem> 
     </asp:DropDownList> 


      <asp:Label ID="lblPhoneHelp" runat="server" AssociatedControlID="ddlPhoneHelp"></asp:Label> 
     <asp:DropDownList ID="ddlPhoneHelp" runat="server"> 
      <asp:ListItem Value="" Text="Choose an option"></asp:ListItem> 
      <asp:ListItem Value="yes" Text="Yes"></asp:ListItem> 
      <asp:ListItem Value="no" Text="No"></asp:ListItem> 
     </asp:DropDownList> 

VB：

Protected Sub ddlHowRec_SelectedIndexChanged(ByVal sender As Object, ByVal e As  System.EventArgs) Handles ddlHowRec.SelectedIndexChanged 

    If ddlHowRec.SelectedValue = "phone" Then 
     lblPhoneHelp.Enabled = False 
    Else 
     lblPhoneHelp.Enabled = True 
    End If 
End Sub 

謝謝

Answer 1

您要停用lblPhoneHelp代替ddlPhoneHelp。

ddlPhoneHelp.Enabled = Not ddlHowRec.SelectedValue = "phone"