c# - Send combination of keystrokes to background window

Question

After a lot of research on Stackoverflow and google, it seems that it's difficult to send a combination of keystroke to a background window using it's handle. For example, I want to send CTRL + F. It seems that Sendmessage doesn't work, and sendinput isn't effective because the window needs the focus.

So the my last thought is about hooking: is there anyway to use that way to send combination?

Answer 1

Ok I found a workaround, but it doesn't work for all applications. Otherwise, it works with puTTY, the program I wanted to control with keystroke combination. And it works even if the application isn't focused. So I'm done now!

class SendMessage
{
[DllImport("user32.dll")]
public static extern IntPtr PostMessage(IntPtr hWnd, uint Msg, IntPtr wParam, IntPtr lParam);

public static void sendKeystroke()
{
    const uint WM_KEYDOWN = 0x100;
    const uint WM_KEYUP = 0x0101;

    IntPtr hWnd;
    string processName = "putty";
    Process[] processList = Process.GetProcesses();

    foreach (Process P in processList)
    {
        if (P.ProcessName.Equals(processName))
        {
            IntPtr edit = P.MainWindowHandle;
            PostMessage(edit, WM_KEYDOWN, (IntPtr)(Keys.Control), IntPtr.Zero);
            PostMessage(edit, WM_KEYDOWN, (IntPtr)(Keys.A), IntPtr.Zero);
            PostMessage(edit, WM_KEYUP, (IntPtr)(Keys.Control), IntPtr.Zero);
        }
    }                           
}

}