Private Sub SaveTreeViewNodes(ByVal nodes As TreeNodeCollection, ByRef list _
      As List(Of TreeNode))
        For Each node As TreeNode In nodes
            list.Add(node)
        Next
    End Sub
 
    Private Sub RestoreTreeViewNode(ByRef list As List(Of TreeNode))
        For Each node As TreeNode In list
            Me.treeDimElements.Nodes.Add(node)
        Next
    End Sub
 
 
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles Button1.Click
        Dim testlist As New List(Of TreeNode)
 
        SaveTreeViewNodes(Me.treeDimElements.Nodes, testlist)
 
        Me.treeDimElements.Nodes.Clear()
 
        RestoreTreeViewNode(testlist)
 
    End Sub