C＃PostMessage到Spotify

Question

I am using C# to find and post the key press of Space (the keyboard shortcut for Pause/Play link ) to the Spotify application. I can successfully find the right window and copy the name of it using the first part of code. But when I try to use the almost exact same code to post the message it won't work. I suspect there is something wrong with the PostMessage part but I can't figure out what.

Code:

private void button1_Click(object sender, EventArgs e)
{
    foreach (System.Diagnostics.Process p in System.Diagnostics.Process.GetProcesses())
    {
        if (p.ProcessName == "Spotify")
        {
            if (!p.MainWindowTitle.StartsWith("Spotify") && p.MainWindowTitle.Length > 0)
            {
                label1.Text = p.MainWindowTitle;
                Console.WriteLine(label1.Text);
                break;
            }
            else
            {
                label1.Text = "No Music";
            }
        }
    }
}

---

[DllImport("user32.dll", SetLastError = true)]
static extern bool PostMessage(IntPtr hWnd, uint msg, IntPtr wParam, IntPtr lParam);

private static Int32 WM_KEYDOWN = 0x0100;
private static Int32 WM_KEYUP = 0x0101;

private void button2_Click(object sender, EventArgs e)
{
    foreach (System.Diagnostics.Process p in System.Diagnostics.Process.GetProcesses())
    {
        if (p.ProcessName == "Spotify")
        {
            Console.WriteLine(p.MainWindowTitle);
            if (p.MainWindowTitle.Length > 0)
            {
                PostMessage(p.MainWindowHandle, (uint)WM_KEYDOWN, (IntPtr)Keys.Space, IntPtr.Zero);
            }
        }
    }
}

Thank you for any help you can provide

/Morgan

Answer 1

Send the key code of the multimedia Play/Pause key instead. The Spotify client listens for that.

See this SO answer for details

Answer 2

Unfortunately for you, Spotify is not a native windows application. It's mostly just a wrapper for Chrome, as far as UI is concerned. This is easily seen when using Spy++ - pressing Space in the Spotify window will not trigger any WM_KEYDOWN message or anything similar.

It may be possible to find some other way of faking this (for example, WM_LBUTTONDOWN seems to be sent properly), but applications avoiding windows messaging are generally much harder to automate.

Fortunately, the application does respond to WM_COMMAND . The following works for me:

PostMessage(hwnd, WM_COMMAND, 0x18007D07, 0x000E0880);

I can't tell you how safe this is, though. wParam will probably stay the same, since that's just the notification code and control ID. I'm not sure about the lParam , though.