Visual Basic: Windows Controls

DropHighlight Property Example

This example adds several Node objects to a TreeView control. After you select a Node object, you can drag it to any other Node. To try the example, place TreeView and ImageList controls on a form and paste the code into the form's Declaration section. Run the example and drag Node objects around to see the result.

Note   The graphics files in the code below can be found on Disk 1 of the Visual Basic or Visual Studio CDs, in the Common\Graphics directory. Change the path in the code, or copy the graphics files to your hard disk before running the code.

' Declare global variables.
Dim indrag As Boolean ' Flag that signals a Drag Drop operation.
Dim nodX As Object ' Item that is being dragged.

Private Sub Form_Load()
   ' Load a bitmap into an Imagelist control.
   Dim imgX As ListImage
   Dim BitmapPath As String
   BitmapPath = "icons\mail\mail01a.ico" ' Change to a valid path.
   Set imgX = imagelist1.ListImages.Add(, , LoadPicture(BitmapPath))
   
   ' Initialize TreeView control and create several nodes.
   TreeView1.ImageList = imagelist1
   Dim nodX As Node   ' Create a tree.
   Set nodX = TreeView1.Nodes.Add(, , , "Parent1", 1)
   Set nodX = TreeView1.Nodes.Add(, , , "Parent2", 1)
   Set nodX = TreeView1.Nodes.Add(1, tvwChild, , "Child 1", 1)
   Set nodX = TreeView1.Nodes.Add(1, tvwChild, , "Child 2", 1)
   Set nodX = TreeView1.Nodes.Add(2, tvwChild, , "Child 3", 1)
   Set nodX = TreeView1.Nodes.Add(2, tvwChild, , "Child 4", 1)
   Set nodX = TreeView1.Nodes.Add(3, tvwChild, , "Child 5", 1)
   nodX.EnsureVisible ' Expand tree to show all nodes.
End Sub

Private Sub TreeView1_MouseDown_
(Button As Integer, Shift As Integer, x As Single, y As Single)
   Set nodX = TreeView1.SelectedItem ' Set the item being dragged.
End Sub

Private Sub TreeView1_MouseMove _
(Button As Integer, Shift As Integer, x As Single, y As Single)
   If Button = vbLeftButton Then ' Signal a Drag operation.
      indrag = True ' Set the flag to true.
      ' Set the drag icon with the CreateDragImage method.
      TreeView1.DragIcon = TreeView1.SelectedItem.CreateDragImage
      TreeView1.Drag vbBeginDrag ' Drag operation.
   End If
End Sub

Private Sub TreeView1_DragDrop_ 
(Source As Control, x As Single, y As Single)
   If TreeView1.DropHighlight Is Nothing Then
      Set TreeView1.DropHighlight = Nothing
      indrag = False
      Exit Sub
   Else
      If nodX = TreeView1.DropHighlight Then Exit Sub
      Cls
      Print nodX.Text & " dropped on " & TreeView1.DropHighlight.Text
      Set TreeView1.DropHighlight = Nothing
      indrag = False
   End If
End Sub

Private Sub TreeView1_DragOver(Source As Control, x As Single, y As Single, State As Integer)
   If indrag = True Then
      ' Set DropHighlight to the mouse's coordinates.
      Set TreeView1.DropHighlight = TreeView1.HitTest(x, y)
   End If
End Sub
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