頁面無法顯示在下拉列表中AutoPostBack

Question

我是ASP.NET新手，請原諒我，如果這是一個簡單的問題。

我正在一個頁面上有一個下拉菜單，在選擇一個選項後，它應該在下面的表格中顯示該數據。當選擇下拉菜單時，我無法顯示頁面。有任何想法嗎？

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代碼：

    Select an Account Number: 

    <asp:DropDownList ID="DropDownList1" runat="server" AppendDataBoundItems="True" 
     AutoPostBack="True" DataSourceID="SqlDataSource1" DataTextField="AccountNumber" 
     DataValueField="AccountNumber"> 
     <asp:ListItem Value="" Text="Select an Account" /><asp:ListItem></asp:ListItem> 
    </asp:DropDownList> 
    &nbsp;<br /> 
    <br /> 
    <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" 
     DataSourceID="SqlDataSource2" CellPadding="4" ForeColor="#333333" 
     GridLines="None"> 
     <AlternatingRowStyle BackColor="White" /> 
     <Columns> 
      <asp:BoundField DataField="BusinessDistrict" HeaderText="BusinessDistrict" 
       SortExpression="BusinessDistrict" /> 
      <asp:BoundField DataField="SurveyDate" HeaderText="SurveyDate" 
       SortExpression="SurveyDate" /> 
      <asp:BoundField DataField="SurveyType" HeaderText="SurveyType" 
       SortExpression="SurveyType" /> 
      <asp:BoundField DataField="Division" HeaderText="Division" 
       SortExpression="Division" /> 
      <asp:BoundField DataField="AccountNumber" HeaderText="AccountNumber" 
       SortExpression="AccountNumber" /> 
      <asp:BoundField DataField="TownCode" HeaderText="TownCode" 
       SortExpression="TownCode" /> 
      <asp:BoundField DataField="Municipality" HeaderText="Municipality" 
       SortExpression="Municipality" /> 
      <asp:BoundField DataField="MeterLocation" HeaderText="MeterLocation" 
       SortExpression="MeterLocation" /> 
      <asp:BoundField DataField="CustomerName" HeaderText="CustomerName" 
       SortExpression="CustomerName" /> 
      <asp:BoundField DataField="MeterNumber" HeaderText="MeterNumber" 
       SortExpression="MeterNumber" /> 
      <asp:BoundField DataField="StreetAddr" HeaderText="StreetAddr" 
       SortExpression="StreetAddr" /> 
     </Columns> 
     <EditRowStyle BackColor="#2461BF" /> 
     <FooterStyle BackColor="#507CD1" Font-Bold="True" ForeColor="White" /> 
     <HeaderStyle BackColor="#507CD1" Font-Bold="True" ForeColor="White" /> 
     <PagerStyle BackColor="#2461BF" ForeColor="White" HorizontalAlign="Center" /> 
     <RowStyle BackColor="#EFF3FB" /> 
     <SelectedRowStyle BackColor="#D1DDF1" Font-Bold="True" ForeColor="#333333" /> 
     <SortedAscendingCellStyle BackColor="#F5F7FB" /> 
     <SortedAscendingHeaderStyle BackColor="#6D95E1" /> 
     <SortedDescendingCellStyle BackColor="#E9EBEF" /> 
     <SortedDescendingHeaderStyle BackColor="#4870BE" /> 
    </asp:GridView> 
    <asp:SqlDataSource ID="SqlDataSource2" runat="server" 
     ConnectionString="<%$ ConnectionStrings:InitialREValveTrackConnectionString %>" 
     SelectCommand="SELECT [BusinessDistrict], [SurveyDate], [SurveyType], 
     [Division], [AccountNumber], [TownCode], [Municipality], [MeterLocation], 
     [CustomerName], [MeterNumber], [StreetAddr] FROM [tbl_Initial] WHERE 
     (([AccountNumber] = @AccountNumber) AND ([MeterNumber] = @MeterNumber))"> 
     <SelectParameters> 
      <asp:ControlParameter ControlID="DropDownList1" DefaultValue="NULL" 
       Name="AccountNumber" PropertyName="SelectedValue" Type="String" /> 
      <asp:ControlParameter ControlID="DropDownList2" DefaultValue="NULL" 
       Name="MeterNumber" PropertyName="SelectedValue" Type="String" /> 
     </SelectParameters> 
    </asp:SqlDataSource> 
$ 

Answer 1

<asp:ControlParameter ControlID="DropDownList2" DefaultValue="NULL" 
      Name="MeterNumber" PropertyName="SelectedValue" Type="String" /> 

你刪除此並重試？如果沒有找到數據，我不確定它會忽略此參數。