在aspx页面中设置div的可见性的问题

Question

我在checkout.aspx页面上有一个div.div的内容如下:

<div id="PaymentDetails" runat="server" style="text-align:center" visible="true">
    <asp:Label ID="PaymentDetailsLbl" Text="Payment Details:" runat="server" Font-Size="Large"></asp:Label>
    <br />
    <br />
    <br />
    <asp:Label ID="UNameLbl" Text="User Name:" runat="server"></asp:Label>
    &nbsp;
    <asp:Label ID="UNameTextLabel" runat="server" Width="150px"></asp:Label>
    <br />
    <br />
    <asp:Label ID="AmountLbl" Text="Amount:" runat="server"></asp:Label>
    &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
    <asp:Label ID="AmountTextLabel" runat="server" Width="50px"></asp:Label>
    <br />
    <br />
    <asp:Label ID="CCNumberLbl" Text="Credit Card No:" runat="server"></asp:Label>
    &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
    <asp:TextBox ID="CCNumberTBox" runat="server"></asp:TextBox>
    <br />
    <br />
    <br />
    <asp:Button ID="SubmitBtn" runat="server" Text="Submit" OnClick="SubmitBtn_Click" />
    <asp:Button ID="ResetBtn" runat="server" OnClick="ResetBtn_Click" Text="Reset" />
    <br />
    <br />
    <asp:Label runat="server" ID="SuccessMessageLabel" ForeColor="Red"></asp:Label>
    <asp:Button ID="SoftwareDownloadsBtn" runat="server" Text="Software Downloads" Visible="false"
        OnClick="SoftwareDownloadsBtn_Click" />
    <br />
    <br />
    <asp:RegularExpressionValidator ID="CCNumberValidator" ErrorMessage="Credit Card Number: Min 10 and max 16 digits, starts with 3 or 4"
        ControlToValidate="CCNumberTBox" runat="server"></asp:RegularExpressionValidator>
</div>

当用户未选择任何项目或用户使用以下代码删除购物车中的所有商品时,我尝试将div的可见性设置为false:

 else if ((Session["SelectedRowItems"] == null) || (shoppingCartItems.Count == 0))
        {
            this.Page.FindControl("PaymentDetails").Visible = false;
            GridView1.EmptyDataText = "No Items Checked Out";
            GridView1.EmptyDataRowStyle.CssClass = "EmptyGridViewContent";
        }

但是我收到以下错误:

你调用的对象是空的.

错误的详细屏幕截图在这里

顺便说一句,我正在使用VS 2008,asp.net/C#及其Web应用程序项目

请帮我.

谢谢你的期待

Answer 1

使用FindControl()定位PaymentDetails如果只有作品PaymentDetails是根容器的一部分.也就是说,它不会递归搜索作为其他控件的子控件的控件.

它似乎FindControl()返回null,当您尝试调用方法时,您会收到错误null.

FindControl()这里没必要.只是用PaymentDetails.Visible = false.