隱藏字段asp.net

Question

我想隱藏GridView中的asp.net中的列，然後使用vb.net訪問GridViewSelectIndexChanged中的值。我在GridView中使用隱藏的字段。當我嘗試訪問使我不要設置在這裏的實例錯誤對象引用的代碼

<asp:GridView ID="GridView1" runat="server" OnSorting="GridView1_OnSorting" AllowPaging="True" AllowSorting="True" 
      AutoGenerateColumns="False" 
      BorderStyle="Outset" CellPadding="4" DataSourceID="odsA02_Tracking" 
      ForeColor="#333333" GridLines="Vertical" Style="border-right: #0000ff thin solid; 
      table-layout: auto; border-top: #0000ff thin solid; font-size: x-small; border-left: #0000ff thin solid; 
      border-bottom: #0000ff thin solid; font-family: Arial; border-collapse: separate" Font-Size="Small" PageSize="30"> 
      <FooterStyle BackColor="#507CD1" Font-Bold="True" ForeColor="White" /> 
      <RowStyle BackColor="#EFF3FB" /> 
      <EditRowStyle BackColor="#2461BF" /> 
      <SelectedRowStyle BackColor="#D1DDF1" Font-Bold="True" ForeColor="#333333" /> 
      <PagerStyle BackColor="#2461BF" ForeColor="White" HorizontalAlign="Center" /> 
      <HeaderStyle BackColor="#507CD1" Font-Bold="True" ForeColor="White" /> 
      <AlternatingRowStyle BackColor="White" /> 
      <Columns> 
       <asp:CommandField ShowSelectButton="True" /> 
       <asp:boundfield datafield="Since" HeaderText="Submit Date" ReadOnly=true SortExpression="Since" /> 

       <asp:BoundField DataField="Started_By" HeaderText="Submitted By" SortExpression="Started_By" /> 
       <asp:BoundField DataField="Client_FullName" HeaderText="Client Name" ReadOnly="True" SortExpression="Client_FullName" /> 
       <asp:BoundField DataField="Product_Desc" HeaderText="Product" ReadOnly="True" SortExpression="Product_Desc" /> 
       <asp:BoundField DataField="Branch_List" HeaderText="Branch" ReadOnly="True" SortExpression="Branch_List" /> 
       <asp:BoundField DataField="Event_AssignedID" HeaderText="Assigned To" ReadOnly="True" 
        SortExpression="Event_AssignedID" /> 
       <asp:BoundField DataField="DaysElapsed" HeaderText="Days Open" ReadOnly="True" SortExpression="DaysElapsed" /> 
       <asp:BoundField DataField="Status" HeaderText="Status" SortExpression="Status" /> 
       <asp:TemplateField HeaderText=Instance_ID > 
       <ItemTemplate> 
       <asp:HiddenField ID=lblInstanceID Value='<%#Eval("Instance_ID") %>' runat=server> 
       </asp:HiddenField> 
       </ItemTemplate> 
       </asp:TemplateField> 
       <asp:TemplateField HeaderText=Seq_ID> 
       <ItemTemplate> 
       <asp:HiddenField ID=lblSeqID Value='<%#Eval("Seq_ID") %>' runat=server/>     
       </ItemTemplate>    

       </asp:TemplateField> 

       <asp:TemplateField HeaderText=Form_Code> 
       <ItemTemplate> 
       <asp:HiddenField ID=lblFormCode Value='<%#Eval("Form_Code") %>' runat=server/>     
       </ItemTemplate>    

       </asp:TemplateField> 



      </Columns> 
     </asp:GridView> 

Protected Sub GridView1_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles GridView1.SelectedIndexChanged 
     Dim Instance_ID As String 
     Dim Seq_ID As String 
     Dim Form_Code As String 
     Dim PARMS As String 
     Dim DestinationURL As String 
     Dim DestinationParms As String 
     Dim instanceID As String = CType(GridView1.FindControl("lblInstanceID"), HiddenField).Value 
End sub 

Answer 1

嘗試僅僅搜索所選行中，像這樣：

Dim instanceID As String = 
CType(GridView1.SelectedRow.FindControl("lblInstanceID"), HiddenField).Value 

而且，是列這些隱藏領域存在隱形？如果它們是，FindControl將不會找到它們。

Answer 2

你可能要考慮使用datakeys代替hiddenfields

http://msdn.microsoft.com/en-us/library/system.web.ui.webcontrols.gridview.datakeys.aspx

使用datakeys將允許你這樣做......

<asp:GridView ID="GridView1" runat="server" datakeynames="instanceID" .../> 

Protected Sub GridView1_SelectedIndexChanges(ByVal sender As Object, ByVal e As System.EventArgs) Handles GridView1.SelectedIndexChanged 
    Dim index As Integer = CustomersGridView.SelectedIndex 
    Dim instanceID As String = GridView1.DataKeys(index).Value.ToString() 
End Sub 

Answer 3

作爲另一個選項，假設你不需要訪問客戶端的值，您可以使用標籤而不是隱藏字段，並將其可見性設置爲false。