List<string> wavlist = new List<string>();
wavlist.Add(Application.StartupPath + "\\mp3\\1.mp3");
wavlist.Add(Application.StartupPath + "\\mp3\\2.mp3");
wavlist.Add(Application.StartupPath + "\\mp3\\3.mp3");
wavlist.Add(Application.StartupPath + "\\mp3\\4.mp3");
foreach (string file in wavlist)
{
WMPLib.WindowsMediaPlayer wplayer = new WMPLib.WindowsMediaPlayer();
wplayer.URL = file;
wplayer.control.play();
}