//1.[DllImport("Kernel32.dll")] //引入命名空间 using System.Runtime.InteropServices;          public static extern bool Beep(int frequency, int duration);// 第一个参数是指频率的高低，越大越高，第二个参数是指响的时间多Beep(500, 700);//2. [DllImport("winmm.dll")]public static extern bool PlaySound(String Filename, int Mod, int Flags);PlaySound(@"C:\Windows\media\Windows Proximity Notification.wav", 0, 1);