很多流行软件都有这样一个选项：Always on Top。它可以让窗口在最上面，别的窗口不能覆盖它。我们在 VB 中，可以使用下面的方法来实现：
Private Const SWP_NOSIZE = &H1
Private Const SWP_NOMOVE = &H2
Private Const SWP_NOZORDER = &H4
Private Const SWP_NOREDRAW = &H8
Private Const SWP_NOACTIVATE = &H10
Private Const SWP_FRAMECHANGED = &H20
Private Const SWP_SHOWWINDOW = &H40
Private Const SWP_NOCOPYBITS = &H80
Private Const SWP_NOOWNERZORDER = &H200
Private Const SWP_DRAWFRAME = SWP_FRAMECHANGED
Private Const SWP_NOREPOSITION = SWP_NOOWNERZORDER
Private Const HWND_TOP = 0
Private Const HWND_BOTTOM = 1
Private Const HWND_TOPMOST = -1
Private Const HWND_NOTOPMOST = -2
Private Declare Function SetWindowPos Lib "user32" ( _
ByVal hwnd As Long, _
ByVal hWndInsertAfter As Long, _
ByVal X As Long, _
ByVal Y As Long, _
ByVal cx As Long, _
ByVal cy As Long, _
ByVal wFlags As Long) As Long
Private mbOnTop As Boolean
Private Property Let OnTop (Setting As Boolean)
if Setting Then
SetWindowPos hwnd, -1, 0, 0, 0, 0, SWP_NOMOVE Or SWP_NOSIZE
Else
SetWindowPos hwnd, -2, 0, 0, 0, 0, SWP_NOMOVE Or SWP_NOSIZE
End If
mbOnTop = Setting
End Property
　
Private Property Get OnTop() As Boolean
'Return the private variable set in Property Let
OnTop = mbOnTop
End Property
调用 OnTop=True 即可让窗口 Always On Top。