Hi Guys, if i've implemented dragdrop code on a treeview to re-arrange the nodes.
I validate the node that i'm attempting to move in the DragOver event.
In final phase of validation, we must ensure that the TreeNode under the cursor is not the TreeNode that is being dragged or a child of that TreeNode. This is important; if we attempt to drop a TreeNode onto itself or a ChildNode, then the node and its siblings would all just vanish.
All node move actions work as expected except where the target node is the node being dragged or child of the dragged node.
The application stops responding.
Any idea why - and how to fix this problem. (Problem possibly with do-loop)
Thanks for any help in advance.
Private Sub tvOptions_DragOver(ByVal sender As Object, ByVal e As System.Windows.Forms.DragEventArgs) Handles tvOptions.DragOver
'Check that there is a TreeNode being dragged
If e.Data.GetDataPresent("System.Windows.Forms.TreeNode", _
True) = False Then Exit Sub
'Get the TreeView raising the event (incase multiple on form)
Dim selectedTreeview As TreeView = CType(sender, TreeView)
'As the mouse moves over nodes, provide feedback to
'the user by highlighting the node that is the
'current drop target
Dim pt As Point = _
CType(sender, TreeView).PointToClient(New Point(e.X, e.Y))
Dim targetNode As TreeNode = selectedTreeview.GetNodeAt(pt)
'See if the targetNode is currently selected,
'if so no need to validate again
If Not (selectedTreeview.SelectedNode Is targetNode) Then
'Select the node currently under the cursor
selectedTreeview.SelectedNode = targetNode
'Check that the selected node is not the dropNode and
'also that it is not a child of the dropNode and
'therefore an invalid target
Dim dropNode As TreeNode = _
CType(e.Data.GetData("System.Windows.Forms.TreeNode"), _
TreeNode)
'If targetNode Is dropNode Then
' e.Effect = DragDropEffects.None
' Exit Sub
'End If
Do Until targetNode Is Nothing
Debug.WriteLine("tvOptions_DragOver, Do-loop")
If targetNode Is dropNode Then
e.Effect = DragDropEffects.None
Exit Sub
End If
targetNode = targetNode.Parent
Loop
End If
'Currently selected node is a suitable target
e.Effect = DragDropEffects.Move
End Sub
I validate the node that i'm attempting to move in the DragOver event.
In final phase of validation, we must ensure that the TreeNode under the cursor is not the TreeNode that is being dragged or a child of that TreeNode. This is important; if we attempt to drop a TreeNode onto itself or a ChildNode, then the node and its siblings would all just vanish.
All node move actions work as expected except where the target node is the node being dragged or child of the dragged node.
The application stops responding.
Any idea why - and how to fix this problem. (Problem possibly with do-loop)
Thanks for any help in advance.
Private Sub tvOptions_DragOver(ByVal sender As Object, ByVal e As System.Windows.Forms.DragEventArgs) Handles tvOptions.DragOver
'Check that there is a TreeNode being dragged
If e.Data.GetDataPresent("System.Windows.Forms.TreeNode", _
True) = False Then Exit Sub
'Get the TreeView raising the event (incase multiple on form)
Dim selectedTreeview As TreeView = CType(sender, TreeView)
'As the mouse moves over nodes, provide feedback to
'the user by highlighting the node that is the
'current drop target
Dim pt As Point = _
CType(sender, TreeView).PointToClient(New Point(e.X, e.Y))
Dim targetNode As TreeNode = selectedTreeview.GetNodeAt(pt)
'See if the targetNode is currently selected,
'if so no need to validate again
If Not (selectedTreeview.SelectedNode Is targetNode) Then
'Select the node currently under the cursor
selectedTreeview.SelectedNode = targetNode
'Check that the selected node is not the dropNode and
'also that it is not a child of the dropNode and
'therefore an invalid target
Dim dropNode As TreeNode = _
CType(e.Data.GetData("System.Windows.Forms.TreeNode"), _
TreeNode)
'If targetNode Is dropNode Then
' e.Effect = DragDropEffects.None
' Exit Sub
'End If
Do Until targetNode Is Nothing
Debug.WriteLine("tvOptions_DragOver, Do-loop")
If targetNode Is dropNode Then
e.Effect = DragDropEffects.None
Exit Sub
End If
targetNode = targetNode.Parent
Loop
End If
'Currently selected node is a suitable target
e.Effect = DragDropEffects.Move
End Sub
