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SetForegroundWindowEx

2006-04-27

Ever found that you can't set the foreground window if you're not the current foreground thread? I was working on StartMenuEx and found that the contextMenuStrip won't close if the window it's being displayed on isn't the foreground window.

Friend Class SetForegroundWindowEx
  Private Declare Function SetForegroundWindow Lib "user32.dll" (ByVal hWnd As IntPtr) As Boolean
  Private Declare Function GetForegroundWindow Lib "user32.dll" () As IntPtr
  Private Declare Function GetWindowThreadProcessId Lib "user32.dll" (ByVal hWnd As IntPtr, ByRef lpdwProcessId As Integer) As Integer
  Private Declare Function GetCurrentThreadId Lib "kernel32.dll" () As Integer
  Private Declare Function AttachThreadInput Lib "user32.dll" (ByVal idAttach As Integer, ByVal idAttachTo As Integer, ByVal fAttach As Boolean) As Boolean

  Public Shared Sub SetForegroundWindowEx(ByVal hWnd As IntPtr)
    Dim foregroundThreadID As Integer
    Dim ourThreadID As Integer
    foregroundThreadID = GetWindowThreadProcessId(GetForegroundWindow(), Nothing)
    ourThreadID = GetCurrentThreadId

    If Not (foregroundThreadID = ourThreadID) Then
      AttachThreadInput(foregroundThreadID, ourThreadID, True) 'attach
      SetForegroundWindow(hWnd) 'set foreground window
      AttachThreadInput(foregroundThreadID, ourThreadID, False) 'detach
    Else
      SetForegroundWindow(hWnd)
    End If
  End Sub
End Class

peace

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