Creating the Form
To demonstrate how to populate a tree view control with links, we will need to create a simple web form. To begin, create a new ASP.NET Empty Web Site and:

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  1. Right click the project in your solution explorer.
  2. Select add new item…
  3. Select a web form.
  4. Name it ‘Default.aspx’.
  5. Click add.
  6. Open Default.aspx up to design mode.
  7. Drag and drop a treeview onto the web form.
  8. Change the ID property to ‘Treeview1′.
  9. Set the AutoGenerateDataBindings property to ‘False’.
  10. Add the following nodes to the treeview:
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    Default.aspx

    The top node of our tree view. 

    <Nodes>
        <asp:TreeNode Value="C:" Text="C:" PopulateOnDemand="true" SelectAction="Select" NavigateUrl="#" >
        </asp:TreeNode>
    </Nodes>

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Once we have our tree view setup we need to add some code that will populate it with some links. To do this, open Default.aspx up to design mode and:

  1. Select the treeview.
  2. Click the Events icon in the Properties window.
  3. Double click the TreeNodePopulate event.
  4. Add the following code to that event method:
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    Default.aspx.vb

    The Treeview1_TreeNodePopulate event method. 

    If IsCallback Then
        If (e.Node.ChildNodes.Count = 0) Then
            Dim node As TreeNode = e.Node
     
            Dim directory As New DirectoryInfo(node.Value)
            Dim s As DirectoryInfo
            Dim fi As FileInfo
            For Each s In directory.GetDirectories()
                Dim subNode As New TreeNode(s.Name)
                subNode.Value = s.FullName
                Try
                    If s.GetDirectories().Length > 0 Or s.GetFiles().Length > 0 Then
                        subNode.SelectAction = TreeNodeSelectAction.SelectExpand
                        subNode.PopulateOnDemand = True
                        subNode.NavigateUrl = "#"
                    End If
                Catch
                    subNode.ImageUrl = "WebResource.axd?a=s&r=TreeView_XP_Explorer_ParentNode.gif&ampt=632242003305625000"
                    node.ChildNodes.Add(subNode)
                End Try
            Next
            For Each fi In directory.GetFiles()
                Dim subNode As New TreeNode(fi.Name)
                node.ChildNodes.Add(subNode)
            Next
        End If
    End If

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Testing
To test this out load up the web site. Ensure that the tree view has some links in it and expands when you click it.
TreeView asp4 vb