Drag and Drop in Treeview

It's all explained here

http://support.microsoft.com/default.aspx?scid=kb;EN-US;307967

It is explained for two separate tree view controls.

Does it work also for within the same treeview?

yep, like this

Public Sub TreeView_ItemDrag(ByVal sender As Object, _
                                  ByVal e As ItemDragEventArgs) _
                                  Handles TreeView1.ItemDrag
        DoDragDrop(e.Item, DragDropEffects.Move)
    End Sub
    Public Sub TreeView_DragEnter(ByVal sender As Object, _
                           ByVal e As DragEventArgs) _
                           Handles TreeView1.DragEnter
        e.Effect = DragDropEffects.Move
    End Sub
    Public Sub TreeView_DragDrop(ByVal sender As Object, _
                                  ByVal e As DragEventArgs) _
                                  Handles TreeView1.DragDrop
        Dim NewNode As TreeNode
        If e.Data.GetDataPresent("System.Windows.Forms.TreeNode", False) Then
            Dim pt As Point
            Dim DestinationNode As TreeNode
            pt = CType(sender, TreeView).PointToClient(New Point(e.X, e.Y))
            DestinationNode = CType(sender, TreeView).GetNodeAt(pt)
            NewNode = CType(e.Data.GetData("System.Windows.Forms.TreeNode"), _
                                            TreeNode)
            'If Not DestinationNode.TreeView Is NewNode.TreeView Then
            DestinationNode.Nodes.Add(NewNode.Clone)
            DestinationNode.Expand()
            'Remove original node
            NewNode.Remove()
            'End If
        End If

For the line:

"e.Effect = DragDropEffects.Move"

I get the following Error message:

Error2: 'Effect' is not a member of 'System.Windows.Forms.ItemDragEventArgs'.      

What to do here?

Sorry, it was my mistake. I already found it.


How can I ensure that drag-drop works only for nodes on the same node level? The hierarchy order must remain intact.

Can you please help me with that issue?

Thanks a lot again!

Hi i_thomas,

What do you mean exactly with the same node level (horizontaly, or verticaly)

I mean the following:

Level 1
    Level2
    Level2
    Level2
         Level3
         Level3
         Level3
         Level3
Level1
Level1
    Level2
    Level2


So If I drag a node from level 2, it should be dropable (insert, not replace!) only on nodes with level 2.

Aha, I'll will try something out, I'll be back :-)

Thanks :-)

If it is difficult for you I offer to raise points to 500!


Regards,

i-Thomas

By the way:

Is it possible to adjust the sensitivity of drag-drop, that means how many pixels I have to drag until this is recognized as a drag-drop operation? If too sensitive, ordinare clicking can cause the start of drag-drop...

this seems to work (but I'll see if I can find a more elegant way)


Public Sub TreeView_DragDrop(ByVal sender As Object, _
                                  ByVal e As DragEventArgs) _
                                  Handles TreeView1.DragDrop
        Dim NewNode As TreeNode
        If e.Data.GetDataPresent("System.Windows.Forms.TreeNode", False) Then
            Dim pt As Point
            Dim DestinationNode As TreeNode
            pt = CType(sender, TreeView).PointToClient(New Point(e.X, e.Y))
            DestinationNode = CType(sender, TreeView).GetNodeAt(pt)
            NewNode = CType(e.Data.GetData("System.Windows.Forms.TreeNode"), _
                                            TreeNode)
            Dim ar1(), ar2() As String
            ar1 = NewNode.FullPath.Split(New Char() {"\"})
            ar2 = DestinationNode.FullPath.Split(New Char() {"\"})
            If ar1.GetUpperBound(0) - 1 = ar2.GetUpperBound(0) Then
                DestinationNode.Nodes.Add(NewNode.Clone)
                DestinationNode.Expand()
                NewNode.Remove()
            End If
        End If


    End Sub

This is much better

Public Function NodeatLevel(ByVal node As TreeNode) As Integer
        Dim level As Integer = 0
        While Not node Is Nothing
            node = node.Parent
            level = level + 1
        End While
        Return level
    End Function

Public Sub TreeView_DragDrop(ByVal sender As Object, _
                                  ByVal e As DragEventArgs) _
                                  Handles TreeView1.DragDrop
        Dim NewNode As TreeNode
        If e.Data.GetDataPresent("System.Windows.Forms.TreeNode", False) Then
            Dim pt As Point
            Dim DestinationNode As TreeNode
            pt = CType(sender, TreeView).PointToClient(New Point(e.X, e.Y))
            DestinationNode = CType(sender, TreeView).GetNodeAt(pt)
            NewNode = CType(e.Data.GetData("System.Windows.Forms.TreeNode"), _
                                            TreeNode)

            Dim level As Integer = NodeatLevel(NewNode) - 1

            If NodeatLevel(DestinationNode) = level Then
                DestinationNode.Nodes.Add(NewNode.Clone)
                DestinationNode.Expand()
                NewNode.Remove()
            End If

        End If


    End Sub

Ok, we are approching the goal. I raised the points to 500.

At the moment I have to drag a Level2 node onto Level1 node and then it "slips" into Level2 position.

I would like to be able to drag a Level2 node directly to the correct position in another Level2 node branch.

Do you get what I mean?

try this (this will insert it under the newly selected node)

Public Sub TreeView_DragDrop(ByVal sender As Object, _
                                  ByVal e As DragEventArgs) _
                                  Handles TreeView1.DragDrop
        Dim NewNode As TreeNode
        If e.Data.GetDataPresent("System.Windows.Forms.TreeNode", False) Then
            Dim pt As Point
            Dim DestinationNode As TreeNode
            pt = CType(sender, TreeView).PointToClient(New Point(e.X, e.Y))
            DestinationNode = CType(sender, TreeView).GetNodeAt(pt)
            NewNode = CType(e.Data.GetData("System.Windows.Forms.TreeNode"), _
                                            TreeNode)
            Dim level As Integer = NodeatLevel(NewNode)
         
            If NodeatLevel(DestinationNode) = level Then
               
                DestinationNode.Parent.Nodes.Insert(DestinationNode.Index + 1, NewNode.Clone)
                DestinationNode.Expand()
             
                NewNode.Remove()
            End If
        End If

Ok, that works.

One last question ;-)


How can I (generally) set the selection focus to a node?

In this current drag and drop case I would like to have the moved node in selected state.

I also wrote "up" and "down" functions for treenodes so that they can be moved up and down within their branch, but I want them to stay selected.

I found "IsSelected", but this seems to be read only...?

this will keep your dragged node selected, the
treeview1.selectnode = 'yournode is the trick

Public Sub TreeView_DragDrop(ByVal sender As Object, _
                                  ByVal e As DragEventArgs) _
                                  Handles TreeView1.DragDrop
        Dim NewNode As TreeNode
        If e.Data.GetDataPresent("System.Windows.Forms.TreeNode", False) Then
            Dim pt As Point
            Dim DestinationNode As TreeNode
            pt = CType(sender, TreeView).PointToClient(New Point(e.X, e.Y))
            DestinationNode = CType(sender, TreeView).GetNodeAt(pt)
            NewNode = CType(e.Data.GetData("System.Windows.Forms.TreeNode"), _
                                            TreeNode)
            Dim level As Integer = NodeatLevel(NewNode)

            If NodeatLevel(DestinationNode) = level Then

                Dim tn As TreeNode = NewNode.Clone
                DestinationNode.Parent.Nodes.Insert(DestinationNode.Index + 1, tn)
                DestinationNode.Expand()
                TreeView1.SelectedNode = tn

                NewNode.Remove()
            End If

        End If


    End Sub

Thanks a lot again!

This was very helpful indeed! Now I think I will manage with the Treeview ;-)

Glad I could help :-)