Dim lst As New List(Of String)_
    ({"a", "a\b", "b", "b\b", "c\a", "c\b", "c\c", "a\c", "a"})
 
For i As Integer = 0 To lst.Count - 1
   Dim parts() As String = lst(i).Split("\"c)
 
   Dim nd() As TreeNode = trv.Nodes.Find(parts(0), False)
   If nd.Length < 1 Then
      trv.Nodes.Add(parts(0), parts(0))
      nd = trv.Nodes.Find(parts(0), False)
   End If
 
   If parts.Length = 2 Then
      Dim snd() As TreeNode = nd(0).Nodes.Find(parts(1), False)
      If snd.Length < 1 Then
         nd(0).Nodes.Add(parts(1), parts(1))
      End If
   End If
Next i