Question

I am trying to capture Window’s active window changed event. Let’s say if user is working on VS and he switches to IE, I want to capture this Active Window Changed Event. I searched on the internet and found many example but nothing seems to work for me.

This is code I have written so far, I am not sure what is wrong in this. I am unable to capture required event through this

class Program
{
    delegate void WinEventDelegate(IntPtr hWinEventHook, uint eventType, IntPtr hwnd, int idObject, int idChild, uint dwEventThread, uint dwmsEventTime);

    [DllImport("user32.dll")]
    static extern IntPtr SetWinEventHook(uint eventMin, uint eventMax, IntPtr hmodWinEventProc, WinEventDelegate lpfnWinEventProc, uint idProcess, uint idThread, uint dwFlags);

    private const uint WINEVENT_OUTOFCONTEXT = 0;
    private const uint EVENT_SYSTEM_FOREGROUND = 3;

    static void Main(string[] args)
    {
        WinEventDelegate dele = new WinEventDelegate(WinEventProc);
        IntPtr m_hhook = SetWinEventHook(EVENT_SYSTEM_FOREGROUND, EVENT_SYSTEM_FOREGROUND, IntPtr.Zero, dele, 0, 0, WINEVENT_OUTOFCONTEXT);
        Console.ReadKey();
    }

    static void WinEventProc(IntPtr hWinEventHook, uint eventType, IntPtr hwnd, int idObject, int idChild, uint dwEventThread, uint dwmsEventTime)
    {
        Console.WriteLine("Something");
    }
}

WinEventProc never gets called, can anybody identify what I am doing wrong programatically or conceptually? I am using Windows 7

Answer 1

You need to be pumping messages to receive WinEvents – and Console.ReadKey() likely doesn’t do this. Try using a MessageBox instead for now to test – and replace with a proper message loop later.

From MSDN:

Remarks:

…

The client thread that calls SetWinEventHook must have a message loop in order to receive events