无人地磅自助机开发总结（六）设置电脑音量大小

1.无人地磅具有语音提示的功能，所以需要根据时间段设置电脑音量大小

2.user32.dll从网上下载下来后需要放入根目录

3.

  [DllImport("user32.dll")]
        public static extern IntPtr SendMessageW(IntPtr hWnd, int Msg, IntPtr wParam, IntPtr lParam);
        public void SetVol()
        {
            p = Process.GetCurrentProcess();
            for (int i = 0; i < 50; i++)
            {
                SendMessageW(p.Handle, WM_APPCOMMAND, p.Handle, (IntPtr)APPCOMMAND_VOLUME_DOWN);
            }
            for (int i = 0; i <25; i++)
            {
                SendMessageW(p.Handle, WM_APPCOMMAND, p.Handle, (IntPtr)APPCOMMAND_VOLUME_UP);
            }
        }

        private Process p;
        private const int APPCOMMAND_VOLUME_MUTE = 0x80000;
        private const int APPCOMMAND_VOLUME_UP = 0x0a0000;
        private const int APPCOMMAND_VOLUME_DOWN = 0x090000;
        private const int WM_APPCOMMAND = 0x319;