NET wrapper/helper that I’ve written for some Windows API functionality. Use the WINEVENT_OUTOFCONTEXT flag to avoid the global-hook problem.Here’s yet another. You can use SetWinEventHook and listen for the EVENT_SYSTEM_FOREGROUND event. Instead of the above make the following modification: public Form1() WinEventDelegate dele = new WinEventDelegate(WinEventProc) //<-causing ERROR This is caused from the line in the Form constructor: public Form1() When running the code you'll notice a crash after a while. I know this thread is old, but for sake of future use: Log.Text += GetActiveWindowTitle() + ' ' Public void WinEventProc(IntPtr hWinEventHook, uint eventType, IntPtr hwnd, int idObject, int idChild, uint dwEventThread, uint dwmsEventTime)

If (GetWindowText(handle, Buff, nChars) > 0) StringBuilder Buff = new StringBuilder(nChars) Static extern int GetWindowText(IntPtr hWnd, StringBuilder text, int count) Static extern IntPtr GetForegroundWindow() Private const uint EVENT_SYSTEM_FOREGROUND = 3 Private const uint WINEVENT_OUTOFCONTEXT = 0 Static extern IntPtr SetWinEventHook(uint eventMin, uint eventMax, IntPtr hmodWinEventProc, WinEventDelegate lpfnWinEventProc, uint idProcess, uint idThread, uint dwFlags) IntPtr m_hhook = SetWinEventHook(EVENT_SYSTEM_FOREGROUND, EVENT_SYSTEM_FOREGROUND, IntPtr.Zero, dele, 0, 0, WINEVENT_OUTOFCONTEXT) ĭelegate void WinEventDelegate(IntPtr hWinEventHook, uint eventType, IntPtr hwnd, int idObject, int idChild, uint dwEventThread, uint dwmsEventTime)

WinEventDelegate dele = null ĭele = new WinEventDelegate(WinEventProc) Create a new windows forms project, add a textbox, make it multiline, and set the textbox Dock property to fill, name it Log and paste in the following code (you'll need to add to your usings).

Getwindowtext msdn