Option Strict On
Imports System.ComponentModel
Public Class TreeViewDraggableNodes
Inherits TreeView
#Region "Events"
Public Event NodeMovedByDrag As EventHandler(Of NodeMovedByDragEventArgs)
Protected Overridable Sub OnNodeMovedByDrag(ByVal e As NodeMovedByDragEventArgs)
RaiseEvent NodeMovedByDrag(Me, e)
End Sub
Public Event NodeMovingByDrag As EventHandler(Of NodeMovingByDragEventArgs)
Protected Overridable Sub OnNodeMovingByDrag(ByVal e As NodeMovingByDragEventArgs)
RaiseEvent NodeMovingByDrag(Me, e)
End Sub
Public Event NodeDraggingOver As EventHandler(Of NodeDraggingOverEventArgs)
Protected Overridable Sub OnNodeDraggingOver(ByVal e As NodeDraggingOverEventArgs)
RaiseEvent NodeDraggingOver(Me, e)
End Sub
#End Region
Sub New()
MyBase.AllowDrop = True
'MyBase.DrawMode = TreeViewDrawMode.OwnerDrawAll
End Sub
<Browsable(False), DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden)> _
Public Shadows ReadOnly Property DrawMode() As System.Windows.Forms.TreeViewDrawMode
Get
Return MyBase.DrawMode
End Get
End Property
'<DefaultValue(True)> _
<Browsable(False), DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden)> _
Public Shadows ReadOnly Property AllowDrop() As Boolean
Get
Return MyBase.AllowDrop
End Get
End Property
Protected Overrides Sub OnItemDrag(ByVal e As System.Windows.Forms.ItemDragEventArgs)
MyBase.DoDragDrop(e.Item, DragDropEffects.Move)
MyBase.OnItemDrag(e)
End Sub
Protected Overrides Sub OnDragOver(ByVal drgevent As System.Windows.Forms.DragEventArgs)
'Get the node we are currently over
'while dragging another node
Dim targetNode As TreeNode = MyBase.GetNodeAt(MyBase.PointToClient(New Point(drgevent.X, drgevent.Y)))
'Get the node being dragged
Dim dragNode As TreeNode = FindNodeInDataObject(drgevent.Data)
Dim eaDraggingOver As New NodeDraggingOverEventArgs(dragNode, targetNode)
OnNodeDraggingOver(eaDraggingOver)
If eaDraggingOver.DropIsLegal = False Then
drgevent.Effect = DragDropEffects.None
Return
End If
'If we are not currently dragging over
'a node...
If targetNode Is Nothing Then
'Let no node be selected
MyBase.SelectedNode = Nothing
'Allow the move because its valid
'to drag a node over the TreeView itself
'the drop will place the node being dragged
'in the root
drgevent.Effect = DragDropEffects.Move
'Get out
Return
End If
'This would only be nothing if something is being
'dragged over the TreeView that isn't a node
If dragNode IsNot Nothing Then
'Illegal to drop nodes inside their descendants
'Its not logical
If targetNode Is dragNode OrElse IsNodeDescendant(targetNode, dragNode) Then
'Prevents a drop
drgevent.Effect = DragDropEffects.None
Else
'Allows a drop
drgevent.Effect = DragDropEffects.Move
MyBase.SelectedNode = targetNode
End If
End If
MyBase.OnDragOver(drgevent)
End Sub
Protected Overrides Sub OnDragDrop(ByVal drgevent As System.Windows.Forms.DragEventArgs)
Dim dragNode As TreeNode = FindNodeInDataObject(drgevent.Data)
If dragNode IsNot Nothing Then
'Dim dragNode As TreeNode = DirectCast(drgevent.Data.GetData(GetType(TreeNode)), TreeNode)
'Get the parent of the node before moving
Dim prevParent As TreeNode = dragNode.Parent
Dim parentToBe As TreeNode = If(MyBase.SelectedNode Is Nothing, Nothing, MyBase.SelectedNode)
Dim eaNodeMoving As New NodeMovingByDragEventArgs(dragNode, prevParent, parentToBe)
OnNodeMovingByDrag(eaNodeMoving)
If eaNodeMoving.CancelMove = False Then
dragNode.Remove()
If MyBase.SelectedNode IsNot Nothing Then
MyBase.SelectedNode.Nodes.Add(dragNode)
Else
MyBase.Nodes.Add(dragNode)
End If
OnNodeMovedByDrag(New NodeMovedByDragEventArgs(dragNode, prevParent))
End If
End If
MyBase.OnDragDrop(drgevent)
End Sub
Private Function IsNodeDescendant(ByVal node As TreeNode, ByVal potentialElder As TreeNode) As Boolean
Dim n As TreeNode
If node Is Nothing OrElse potentialElder Is Nothing Then Return False
Do
n = node.Parent
If n IsNot Nothing Then
If n Is potentialElder Then
Return True
Else
node = n
End If
End If
Loop Until n Is Nothing
Return False
End Function
Private Function FindNodeInDataObject(ByVal dataObject As IDataObject) As TreeNode
For Each format As String In dataObject.GetFormats
Dim data As Object = dataObject.GetData(format)
If GetType(TreeNode).IsAssignableFrom(data.GetType) Then
Return DirectCast(data, TreeNode)
End If
Next
Return Nothing
End Function
End Class
Public Class NodeDraggingOverEventArgs
Inherits EventArgs
Private _DropLegal As Boolean
Private _MovingNode As TreeNode
Private _TargetNode As TreeNode
Public Sub New(ByVal movingNode As TreeNode, ByVal targetNode As TreeNode)
_DropLegal = True
_MovingNode = movingNode
_TargetNode = targetNode
End Sub
Public ReadOnly Property TargetNode() As TreeNode
Get
Return _TargetNode
End Get
End Property
Public ReadOnly Property MovingNode() As TreeNode
Get
Return _MovingNode
End Get
End Property
'Use this to disallow a drop
Public Property DropIsLegal() As Boolean
Get
Return _DropLegal
End Get
Set(ByVal value As Boolean)
_DropLegal = value
End Set
End Property
End Class
Public Class NodeMovingByDragEventArgs
Inherits EventArgs
Private _MovingNode As TreeNode
Private _CurParent As TreeNode
Private _ParentToBe As TreeNode
Private _CancelMove As Boolean
Public Sub New(ByVal nodeMoving As TreeNode, ByVal prevParent As TreeNode, ByVal parentToBe As TreeNode)
_MovingNode = nodeMoving
_CurParent = prevParent
_ParentToBe = parentToBe
End Sub
Public Property CancelMove() As Boolean
Get
Return _cancelMove
End Get
Set(ByVal value As Boolean)
_CancelMove = value
End Set
End Property
Public ReadOnly Property MovingNode() As TreeNode
Get
Return _MovingNode
End Get
End Property
Public ReadOnly Property CurrentParent() As TreeNode
Get
Return _CurParent
End Get
End Property
Public ReadOnly Property ParentToBe() As TreeNode
Get
Return _ParentToBe
End Get
End Property
End Class
Public Class NodeMovedByDragEventArgs
Inherits EventArgs
Private _MovedNode As TreeNode
Private _PreviousParent As TreeNode
Public Sub New(ByVal nodeMoved As TreeNode, ByVal prevParent As TreeNode)
_MovedNode = nodeMoved
_PreviousParent = prevParent
End Sub
Public ReadOnly Property MovedNode() As TreeNode
Get
Return _MovedNode
End Get
End Property
Public ReadOnly Property PreviousParent() As TreeNode
Get
Return _PreviousParent
End Get
End Property
End Class
[RESOLVED] TreeView Drag and Drop Node Placement
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Originally Posted by BMWessel
