TreeView

tr=Master.FindControl("NavigationTree") as TreeView;;

//tr = new TreeView();

//tr =

//(TreeView)this.Master.FindControl("NavigationTree");

Label1.Text = tr.SelectedNode.NavigateUrl;

above code is not working(object reference is not set to an instance of the object)

How to access the navigateurl of

child of treeview in masterpage

to content page?

Master Page

<%

@ master language="C#" %>

<

html xmlns="http://www.w3.org/1999/xhtml">

<

head id="Head1" runat="Server">

<title>Web Site</title>

</

head>

<

body>

<

form id="Form1" runat="Server">

<

table border="1">

<

tr>

<td style="width:140px; vertical-align:top; background-color:#E0E0E0">

<b>Menu</b><br/>

<asp:TreeView id="NavigationTree" Runat="Server"

HoverNodeStyle-Font-Bold="True" RootNodeStyle-ForeColor="Blue">

<Nodes>

<asp:TreeNode Text="Page 1" NavigateUrl="Page1.aspx" Target="frame3">

<asp:TreeNode Text="Page 1-1" />

<asp:TreeNode Text="Page 1-2" />

</asp:TreeNode>

<asp:TreeNode Text="Page 2" >

<asp:TreeNode Text="Page 2-1"/>

<asp:TreeNode Text="Page 2-2"/>

</asp:TreeNode>

<asp:TreeNode Text="Page 3" >

<asp:TreeNode Text="Page 3-1"/>

<asp:TreeNode Text="Page 3-2">

<asp:TreeNode Text="Page 3-2-1"/>

<asp:TreeNode Text="Page 3-2-2"/>

</asp:TreeNode>

</asp:TreeNode>

</Nodes>

</asp:TreeView>

</td>

<td style="width:350px; vertical-align:top">

<asp:ContentPlaceHolder id="CONTENT" Runat="Server"/>

</td>

</

tr>

</

table>

</

form>

</

body>

</

html>

 Where are you running this:

TreeView tr=Master.FindControl("NavigationTree") as TreeView;; 
//(TreeView)this.Master.FindControl("NavigationTree"); 
Label1.Text = tr.SelectedNode.NavigateUrl;

 ?

It should work, unless your content page is not using the master page you have specified above.

 

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Debugger is my best friend.

Are you sure tr.SelectedNode is pointing to some node when you try to access its NavigateUrl? If a TreeNode is selected and it has NavigateUrl defined, then after selecting the TreeNode you'll be redirected to the Url defined in NavigateUrl, even if the NavigateUrl is pointing current page, the TreeNode will be re-initialized to unselected so the object reference not set exception comes out.

Workaround here should be using something like ViewState or Session, here are some useful links:

ASP.NET State Management Recommendations
How to: Pass Values Between ASP.NET Web Pages

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