how to get treeview nodes value in asp.net

As your question is not that much clear to give you a proper solution still i am trying here to give you some choices to get the solution or a hint to your solution.

Let say my TreeView name is 'tvTest'. Now the design for it is :-

<asp:treeview runat="server" id="tvTest" xmlns:asp="#unknown">
        <nodes>
            <asp:treenode text="Item 1">
                <asp:treenode text="Item 1.1"></asp:treenode>
                <asp:treenode text="Item 1.2"></asp:treenode>
                <asp:treenode text="Item 1.3"></asp:treenode>
            </asp:treenode>
            <asp:treenode text="Item 2">
                <asp:treenode text="Item 2.1"></asp:treenode>
                <asp:treenode text="Item 2.2"></asp:treenode>
            </asp:treenode>
            
            <asp:treenode text="Item 3">
                <asp:treenode text="Item 3.1"></asp:treenode>
            </asp:treenode>
        </nodes>
    </asp:treeview>

To get SelectedNode value only we can go by two ways like :-

tvTest.SelectedValue
tvTest.SelectedNode.Value

To get the selected node text :-

tvTest.SelectedNode.Text

To get the path for the values from parent to current :-

tvTest.SelectedNode.ValuePath

Hope this will be of help to you.
Please let me know if you need help on any other way ?