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Modify the order of a treeview control during runtime?

I have a treeview control on a custom task pane in Excel. I've enable the ability to use Drag & Drop (by following this how-to) on the treeview to change the order of the nodes. The problem though is if I close the application and then go back in, the nodes are back in the order they were before I had reordered them. Is there a way that I can modify my DragDrop event to permanently change the index of the nodes?

Here's my code if you're interested. It's almost literally a copy and paste job from the site that I linked to above:

Expand|Select|Wrap|Line Numbers
  1. Private Sub ManningFiltersTreeView_DragDrop(ByVal sender As Object, ByVal e As System.Windows.Forms.DragEventArgs) Handles ManningFiltersTreeView.DragDrop
  3.         'Check that there is a TreeNode being dragged
  4.         If e.Data.GetDataPresent("System.Windows.Forms.TreeNode", _
  5.               True) = False Then Exit Sub
  7.         'Get the TreeView raising the event (incase multiple on form)
  8.         Dim selectedTreeview As TreeView = CType(sender, TreeView)
  10.         'Get the TreeNode being dragged
  11.         Dim dropNode As TreeNode = _
  12.               CType(e.Data.GetData("System.Windows.Forms.TreeNode"),  _
  13.               TreeNode)
  15.         'The target node should be selected from the DragOver event
  16.         Dim targetNode As TreeNode = selectedTreeview.SelectedNode
  18.         'Remove the drop node from its current location
  19.         dropNode.Remove()
  21.         'If there is no targetNode add dropNode to the bottom of
  22.         'the TreeView root nodes, otherwise add it to the end of
  23.         'the dropNode child nodes
  24.         If targetNode Is Nothing Then
  25.             selectedTreeview.Nodes.Add(dropNode)
  26.         Else
  27.             targetNode.Nodes.Add(dropNode)
  28.         End If
  30.         'Ensure the newly created node is visible to
  31.         'the user and select it
  32.         dropNode.EnsureVisible()
  33.         selectedTreeview.SelectedNode = dropNode
  35.     End Sub
  37.     Private Sub ManningFiltersTreeView_DragEnter(ByVal sender As Object, ByVal e As System.Windows.Forms.DragEventArgs) Handles ManningFiltersTreeView.DragEnter
  39.         'See if there is a TreeNode being dragged
  40.         If e.Data.GetDataPresent("System.Windows.Forms.TreeNode", _
  41.             True) Then
  42.             'TreeNode found allow move effect
  43.             e.Effect = DragDropEffects.Move
  44.         Else
  45.             'No TreeNode found, prevent move
  46.             e.Effect = DragDropEffects.None
  47.         End If
  49.     End Sub
  51.     Private Sub ManningFiltersTreeView_DragOver(ByVal sender As Object, ByVal e As System.Windows.Forms.DragEventArgs) Handles ManningFiltersTreeView.DragOver
  53.         'Check that there is a TreeNode being dragged 
  54.         If e.Data.GetDataPresent("System.Windows.Forms.TreeNode", _
  55.                True) = False Then Exit Sub
  57.         'Get the TreeView raising the event (incase multiple on form)
  58.         Dim selectedTreeview As TreeView = CType(sender, TreeView)
  60.         'As the mouse moves over nodes, provide feedback to 
  61.         'the user by highlighting the node that is the 
  62.         'current drop target
  63.         Dim pt As Point = _
  64.             CType(sender, TreeView).PointToClient(New Point(e.X, e.Y))
  65.         Dim targetNode As TreeNode = selectedTreeview.GetNodeAt(pt)
  67.         'See if the targetNode is currently selected, 
  68.         'if so no need to validate again
  69.         If Not (selectedTreeview.SelectedNode Is targetNode) Then
  70.             'Select the    node currently under the cursor
  71.             selectedTreeview.SelectedNode = targetNode
  73.             'Check that the selected node is not the dropNode and
  74.             'also that it is not a child of the dropNode and 
  75.             'therefore an invalid target
  76.             Dim dropNode As TreeNode = _
  77.                 CType(e.Data.GetData("System.Windows.Forms.TreeNode"),  _
  78.                 TreeNode)
  80.             Do Until targetNode Is Nothing
  81.                 If targetNode Is dropNode Then
  82.                     e.Effect = DragDropEffects.None
  83.                     Exit Sub
  84.                 End If
  85.                 targetNode = targetNode.Parent
  86.             Loop
  87.         End If
  89.         'Currently selected node is a suitable target
  90.         e.Effect = DragDropEffects.Move
  91.         'End If
  93.     End Sub
  95.     Private Sub ManningFiltersTreeView_ItemDrag(ByVal sender As Object, ByVal e As System.Windows.Forms.ItemDragEventArgs) Handles ManningFiltersTreeView.ItemDrag
  97.         'Set the drag node and initiate the DragDrop 
  98.         DoDragDrop(e.Item, DragDropEffects.Move)
  100.     End Sub
Oct 19 '08 #1
3 4309
I received a response in a different forum. I wanted to include it here because I'm hoping someone might be able to help me implement the solution. The response was:

You'd need to save the status when the control is removed from memory, then restore it in the code that's initializing the control (when the task pane is being displayed the first time).

The better place to ask this kind of question would be a forum that specializes in working with Windows Forms and their controls. The specialists there should be able to tell you the most efficient way to save the state of the control, then restore it at a later point.
So if I understand this correctly, I need to save the status of the treeview control by writing it to a file (or another spreadsheet? (yes, this is in Excel using Visual Studio Tools for Office) before closing the workbook and then when the workbook is reopened it needs to read that data back into the control to display it's last state? Could this be done by databinding the treeview control to an Excel table? or would it be better to use some sort of XML file to better represent the heirarchy of the treeview control?

Does anyone have any idea how to do this?
Oct 20 '08 #2
Okay, here's an idea everyone. What if on the thisworkbook_shutdown event, I looped through the tree and extracted the text and fullpath properties of each node and added them to a Text and Path array and then wrote both arrays to a blank worksheet.

And then as part of the thisworkbook_startup event, I read through the range on my blank worksheet and added a node to the treeview and assigned each new node the fullpath property.

So far I've got it working to write the status of my treeview to the spreadsheet. Here's the code that I'm using up to this point:

Expand|Select|Wrap|Line Numbers
  1.         Dim Text As New List(Of String)
  2.         Dim Path As New List(Of String)
  4.         'Call the ExtractTextFromNodes function.  This finds all the text and fullpath properties of each node in the treeview and adds them to
  5.         'a an array.
  6.         ExtractTextFromNodes(APPredator.ManningFiltersTreeView.Nodes, Text, Path)
  9.         Dim int As Integer = 0
  11.         For i = 1 To Text.Count
  12.             CType(Globals.ThisWorkbook.Sheets("Manning Config"), Excel.Worksheet).Range("BV" & i).Value2 = Text(int)
  13.             int = int + 1
  14.         Next
  16.         int = 0
  17.         For i = 1 To Path.Count
  18.             CType(Globals.ThisWorkbook.Sheets("Manning Config"), Excel.Worksheet).Range("BW" & i).Value2 = Path(int)
  19.             int = int + 1
  20.         Next
  22. Private Shared Sub ExtractTextFromNodes(ByVal nodeList As TreeNodeCollection, ByVal Text As List(Of String), ByVal Path As List(Of String))
  24.         Dim n As TreeNode
  26.         For Each n In nodeList
  29.             Text.Add(n.Text)
  30.             Path.Add(n.FullPath)
  31.             ExtractTextFromNodes(n.Nodes, Text, Path)
  34.         Next
  36.     End Sub
Next step is to read the data from my spreadsheet and build a treeview from it. If I've gone off track with this idea, let me know. If there's an easier way to do it, let me know too. :)
Oct 20 '08 #3
I've got this working now. The solution is found here .
Oct 30 '08 #4

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