Program is unresponsive for a couple of seconds
<p>I found a way to capture the <code>Print Screen</code> button in C#. When pressing <code>Alt + Print Screen</code> a simple messagebox pops up saying the keys have been pressed. <strong>But</strong> it's unresponsive for a couple of seconds right after. I have no idea why this is happening.</p>

<p>Here's the code I use:</p>

<pre><code>static class Program
{
    /// &lt;summary&gt;
    /// The main entry point for the application.
    /// &lt;/summary&gt;
    [STAThread]
    static void Main()
    {
        Application.EnableVisualStyles();
        Application.SetCompatibleTextRenderingDefault(false);
        _hookID = SetHook(_proc);
        Application.Run(new Form1());
        UnhookWindowsHookEx(_hookID);  
    }

    /****************************************/
    private const int WH_KEYBOARD_LL = 13;
    //private const int WH_KEYBOARD_LL = 13;  
    private const int WM_KEYDOWN = 0x0100;
    private const int VK_F1 = 0x70;
    private static LowLevelKeyboardProc _proc = HookCallback;
    private static IntPtr _hookID = IntPtr.Zero;

    private static IntPtr SetHook(LowLevelKeyboardProc proc)
    {
        using (Process curProcess = Process.GetCurrentProcess())
        using (ProcessModule curModule = curProcess.MainModule)
        {
            return SetWindowsHookEx(WH_KEYBOARD_LL, proc,
                GetModuleHandle(curModule.ModuleName), 0);
        }
    }

    private delegate IntPtr LowLevelKeyboardProc(
        int nCode, IntPtr wParam, IntPtr lParam);

    private static IntPtr HookCallback(
        int nCode, IntPtr wParam, IntPtr lParam)
    {

        if (nCode &gt;= 0)
        {
            Keys number = (Keys)Marshal.ReadInt32(lParam);
            if (number == Keys.PrintScreen)
            {
                if ((wParam == (IntPtr)260 &amp;&amp; Keys.Alt == Control.ModifierKeys &amp;&amp; number == Keys.PrintScreen))
                {
                    MessageBox.Show("You pressed alt+ print screen");
                }
            }

        }
        return CallNextHookEx(IntPtr.Zero, nCode, wParam, lParam);

    }

    [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
    private static extern IntPtr SetWindowsHookEx(int idHook,
        LowLevelKeyboardProc lpfn, IntPtr hMod, uint dwThreadId);

    [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
    [return: MarshalAs(UnmanagedType.Bool)]
    private static extern bool UnhookWindowsHookEx(IntPtr hhk);

    [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
    private static extern IntPtr CallNextHookEx(IntPtr hhk, int nCode,
        IntPtr wParam, IntPtr lParam);

    [DllImport("kernel32.dll", CharSet = CharSet.Auto, SetLastError = true)]
    private static extern IntPtr GetModuleHandle(string lpModuleName); 
}
</code></pre>

<p>Does anyone have a clue why it's hanging after the messagebox?</p>
