C# 从弹出窗口访问asp内容

我想从弹出窗口访问asp树视图。我把它公之于众，这样我就可以访问它。 智利或弹出页面中的代码

SomeWebPage FlViewPage = new SomeWebPage(); 
lblMessage.Text = FlViewPage.TreeView1.Nodes.Count.ToString();

问题是，当我运行该网站时，出现了一个错误：

Object reference not set to an instance of an object.

网页（从中调用弹出窗口）代码树将动态填充

    <%@ Page Title="Folder View" Language="C#" MasterPageFile="~/Site.Master" AutoEventWireup="true" CodeBehind="FolderView.aspx.cs" Inherits="SwimWebFile.FolderView" %>
<div id="content"> <div class="post">
<h1 class="title"> <asp:Label ID="lblTitle" runat="server" Text="Documents"></asp:Label></h1>
    <div class="entry" >
     <!-- Center the pop window in the middle -->
        <script type="text/javascript">
            function PopupCenter(pageURL, title, w, h) {
                var left = (screen.width / 2) - (w / 2);
                var top = (screen.height / 2) - (h / 2);
                var targetWin = window.open(pageURL, title, 'toolbar=no, location=no, directories=no, status=no, menubar=no, scrollbars=no, resizable=no, copyhistory=no, width=' + w + ', height=' + h + ', top=' + top + ', left=' + left);
            } 
        </script>
        <a href="javascript:void(0);" onclick="PopupCenter('NewFolderPopup.aspx', 'Add Document',340,185);">Click Here for Upload</a>
        <font size="4">
        <asp:TreeView ID="TreeViewDocuments" runat="server" ExpandDepth="0" 
            ImageSet="Simple" Visible="False" onprerender="TreeView_PreRender">
            <HoverNodeStyle Font-Underline="True" ForeColor="#5555DD" />
            <LeafNodeStyle NodeSpacing="10px" />
            <Nodes>
                <asp:TreeNode Text="System" Value="Systems" Expanded="False" 
                    SelectAction="Expand">
                </asp:TreeNode>
                <asp:TreeNode Text="Document" Value="Documents" Expanded="False" 
                    SelectAction="Expand">
                </asp:TreeNode>
            </Nodes>
            <NodeStyle Font-Names="Tahoma" Font-Size="Medium" ForeColor="Black" 
                HorizontalPadding="0px" NodeSpacing="7px" VerticalPadding="0px" />
            <ParentNodeStyle Font-Bold="False" />
            <SelectedNodeStyle Font-Underline="True" ForeColor="#5555DD" 
                HorizontalPadding="0px" VerticalPadding="0px" />
        </asp:TreeView>
            <asp:Button ID="btnNewFolder" runat="server" Text="New Folder" 
            onclick="btnNewFolder_Click" UseSubmitBehavior="False"/>
            <asp:Button ID="btnRenameFolder" runat="server" Text="Rename Folder" />
            <asp:Button ID="btnDeleteFolder" runat="server" Text="Delete Folder" />
   </font></div>
</div>

错误

    Server Error in '/' Application.

Object reference not set to an instance of an object.

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. 

Exception Details: System.NullReferenceException: Object reference not set to an instance of an object.

Source Error: 

Line 56:             FolderView FlViewPage = new FolderView();
Line 57:             lblMessage.Text = FlViewPage.TreeViewDocuments.Nodes.Count.ToString();

Stack Trace: 

[NullReferenceException: Object reference not set to an instance of an object.]
   SwimWebFile.NewFolderPopup.btnCreate_Click(Object sender, EventArgs e) in C:\Users\...\NewFolderPopup.aspx.cs:57
   System.Web.UI.WebControls.Button.OnClick(EventArgs e) +118
   System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument) +112
   System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument) +10
   System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) +13
   System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) +36
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +5563

---

有很多可能是空的，我会连接一个调试器到它，看看什么是空的。此时，我的猜测是Treeview1或FlViewPage，但我可能没有完整的图片

我找到了解决此问题的方法。我使用该方法只接收值，而不是整个树视图

---

谢谢你的建议

是的，这很让人困惑，因为树视图已经在某个网页中填充，所以我不知道为什么不能传递它的参数或节点。你能发布某个网页的外观吗？代码添加。从FolderView.aspx调用BtnewFolder时，弹出窗口打开。我想把TreeView节点放到这个弹出窗口。你能发布你得到的异常调用堆栈吗？添加了堆栈跟踪。我只需要输入“.count”来查看是否可以在网页之间传输一些值。

    Server Error in '/' Application.

Object reference not set to an instance of an object.

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. 

Exception Details: System.NullReferenceException: Object reference not set to an instance of an object.

Source Error: 

Line 56:             FolderView FlViewPage = new FolderView();
Line 57:             lblMessage.Text = FlViewPage.TreeViewDocuments.Nodes.Count.ToString();

Stack Trace: 

[NullReferenceException: Object reference not set to an instance of an object.]
   SwimWebFile.NewFolderPopup.btnCreate_Click(Object sender, EventArgs e) in C:\Users\...\NewFolderPopup.aspx.cs:57
   System.Web.UI.WebControls.Button.OnClick(EventArgs e) +118
   System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument) +112
   System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument) +10
   System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) +13
   System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) +36
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +5563