Binaryworld - Limit the length of the text in a TreeView node ... [ VB -> Controls-TreeView ]

The TreeView control doesn't expose any property that lets you limit the amount of text users can type when editing a Node's label. However, you can do the trick with a couple of SendMessage API calls from within the BeforeLabelEdit event: with the TVM_GETEDITCONTROL message you retrieve the handle of the hidden Edit control that the TreeView creates for let the user edit the node. If you then send the EM_LIMITTEXT message to this Edit control you can put a limit to the text that can be typed in this control:

Click here to copy the following block

Private Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal _
  hWnd As Long, ByVal wMsg As Long, ByVal wParam As Long, _
  lParam As Any) As Long
Const TV_FIRST = &H1100
Const TVM_GETEDITCONTROL = TV_FIRST + 15
Const EM_LIMITTEXT = &HC5

' limit the text that can be typed in TreeView1's node to 20 characters

Private Sub TreeView1_BeforeLabelEdit(Cancel As Integer)
  Dim editHWnd As Long
  ' get the handle of the TreeView's Edit control
  editHWnd = SendMessage(TreeView1.hWnd, TVM_GETEDITCONTROL, 0, ByVal 0&)
  ' send it a EM_LIMITTEXT message to limit its length
  SendMessage editHWnd, EM_LIMITTEXT, 20, 0
End Sub

Once you now the method you can perform some other tricks with the Edit control. For example, you can automatically convert all text to uppercase:

Click here to copy the following block

Private Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal _
  hWnd As Long, ByVal wMsg As Long, ByVal wParam As Long, _
  lParam As Any) As Long
Private Declare Function SetWindowLong Lib "user32" Alias "SetWindowLongA" _
  (ByVal hWnd As Long, ByVal nIndex As Long, ByVal dwNewLong As Long) As Long
Private Declare Function GetWindowLong Lib "user32" Alias "GetWindowLongA" _
  (ByVal hWnd As Long, ByVal nIndex As Long) As Long
Private Const GWL_STYLE = (-16)

Const TV_FIRST = &H1100
Const TVM_GETEDITCONTROL = TV_FIRST + 15
Const ES_UPPERCASE = &H8&

' force the text typed in a TreeView's node to uppercase

Private Sub TreeView1_BeforeLabelEdit(Cancel As Integer)
  Dim editHWnd As Long

  ' get the handle of the TreeView's Edit control
  editHWnd = SendMessage(TreeView1.hWnd, TVM_GETEDITCONTROL, 0, ByVal 0&)
  ' force the all-uppercase style
  SetWindowLong editHWnd, GWL_STYLE, GetWindowLong(editHWnd, _
    GWL_STYLE) Or ES_UPPERCASE
End Sub