值不能为空.参数名称:control

Question

我曾经使用UpdatePanel作为整个Listview项的包装器。

<asp:UpdatePanel ID="UpdatePanel1" runat="server">
    <ContentTemplate>
        <asp:ListView ID="ListView1" runat="server">
            <LayoutTemplate>
                <asp:PlaceHolder id="itemPlaceholder" runat="server" />
            </LayoutTemplate>
            <ItemTemplate> 
                '....
            </ItemTemplate>
        </asp:ListView>
    </ContentTemplate>
 <Triggers></Triggers>
</asp:UpdatePanel>

并按如下方式注册客户端脚本…

 Private Sub ListView1_ItemCommand(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.ListViewCommandEventArgs) Handles ListView1.ItemCommand
    if Not ClientScript.IsClientScriptBlockRegistered(Me.[GetType](), "OtherScript") Then
       ScriptManager.RegisterStartupScript(DirectCast(Page.FindControl("UpdatePanel1"), UpdatePanel), GetType(String), "alertScript", "update('hpClips','false','inc')", True)
    End If
 End sub

现在我决定只包装ImageButtons组与更新面板如下…

<asp:ListView ID="ListView1" runat="server">
    <LayoutTemplate>
        <asp:PlaceHolder id="itemPlaceholder" runat="server" />
    </LayoutTemplate>
    <ItemTemplate> 
        <asp:UpdatePanel ID="UpdatePanel1" runat="server" UpdateMode="Always" RenderMode="Block">
            <ContentTemplate>
                <asp:ImageButton ID="btnAttach" runat="server" CommandName='<%# "AddC_" & Eval("QID") & "_" & Eval("Label") %>'/>
                <asp:ImageButton ID="btnFavorite" runat="server" CommandName='<%# "AddF_" & Eval("QID")  & "_" & Eval("Label") %>'/>
            </ContentTemplate>
        </asp:UpdatePanel>
    </ItemTemplate>
</asp:ListView>

，我得到以下错误

Value cannot be null. Parameter name: control

执行ScriptManager.RegisterStartupScript(DirectCast(Page.FindControl("UpdatePanel1"), UpdatePanel), GetType(String), "alertScript", "update('hpClips','false','inc')", True)

我认为这与没有找到updatepanel控件的事实有关。直接强制转换抛出异常。那我该怎么解决呢?提前谢谢你。

更新:我也试过这个。(这一次，我没有得到异常，但客户端脚本没有执行)

Private Sub ListView1_ItemCommand(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.ListViewCommandEventArgs) Handles ListView1.ItemCommand
    Dim UpdPanel As New UpdatePanel
    For Each Up As UpdatePanel In e.Item.Controls.OfType(Of UpdatePanel)()
           UpdPanel = Up             
    Next
    if Not ClientScript.IsClientScriptBlockRegistered(Me.[GetType](), "OtherScript") Then
       ScriptManager.RegisterStartupScript(DirectCast(UpdPanel, UpdatePanel), GetType(String), "alertScript", "update('hpClips','false','inc')", True)
    End If
End sub

Answer 1

修复!下面的代码实现了这个技巧

If Not ClientScript.IsClientScriptBlockRegistered(Me.[GetType](), "OtherScript") Then
 ScriptManager.RegisterStartupScript(Me.Page, Me.GetType(), Guid.NewGuid.ToString, "update('hpClips','false','inc')", True)
End If

有帮助的资源

ScriptManager的问题。注册startpscript在WebControl中嵌套在UpdatePanel

在异步回发期间使用RegisterStartupScript以编程方式添加JavaScript