C#没有提供播放MP3等音频文件的类，要编写播放MP3等音频文件程序，必须使用第三方控件或类。本文使用API函数mciSendString，编写一个播放MP3等音频文件的类。

具体源码如下：

一、使用API函数mciSendString构成的媒体播放类。

using System;

using System.Runtime.InteropServices;

using System.Text;

using System.IO ;

namespace clsMCIPlay

{

　 /// <summary>

　 /// clsMci 的摘要说明。

　 /// </summary>

　 public class clsMCI

　 {

public clsMCI()

{

　 //

　 // TODO: 在此处添加构造函数逻辑

　 //

}

//定义API函数使用的字符串变量

[MarshalAs(UnmanagedType.ByValTStr,SizeConst=260)]

private string Name = "" ;

[MarshalAs(UnmanagedType.ByValTStr,SizeConst=128)]

private string durLength = "" ;

[MarshalAs(UnmanagedType.LPTStr,SizeConst=128)]

private string TemStr ="";

int ilong;

//定义播放状态枚举变量

public enum State

{

　 mPlaying = 1,

　 mPuase = 2,

　 mStop = 3

};

//结构变量

public struct structMCI

{

　 public bool bMut;

　 public int iDur;

　 public int iPos;

　 public int iVol;

　 public int iBal;

　 public string iName;

　 public State state;

};

public structMCI mc =new structMCI() ;

//取得播放文件属性

public string FileName

{

　 get

　 {

return mc.iName;

　 }

　 set

　 {

//ASCIIEncoding asc = new ASCIIEncoding();

try

{

　 TemStr ="";

　 TemStr = TemStr.PadLeft(127,Convert.ToChar(" "));

　 Name = Name.PadLeft(260,Convert.ToChar(" ")) ;

　 mc.iName = value;

　 ilong = APIClass.GetShortPathName(mc.iName,Name, Name.Length);

　 Name = GetCurrPath(Name);

　 //Name = "open " + Convert.ToChar(34) + Name + Convert.ToChar(34) + " alias media";

　 Name = "open " + Convert.ToChar(34) + Name + Convert.ToChar(34) + " alias media";

　 ilong = APIClass.mciSendString("close all", TemStr, TemStr.Length , 0);

　 ilong = APIClass.mciSendString( Name, TemStr, TemStr.Length, 0);

　 ilong = APIClass.mciSendString("set media time format milliseconds", TemStr, TemStr.Length , 0);

　 mc.state = State.mStop;

}

catch

{

　 MessageBox.Show("出错错误!");

}

　 }

}

//播放

public void play()

{

　 TemStr = "";

　 TemStr = TemStr.PadLeft(127,Convert.ToChar(" "));

　 APIClass.mciSendString("play media", TemStr, TemStr.Length , 0);

　 mc.state = State.mPlaying ;

}

//停止

public void StopT()

{

　 TemStr = "";

　 TemStr = TemStr.PadLeft(128,Convert.ToChar(" "));

　 ilong = APIClass.mciSendString("close media", TemStr, 128, 0);

　 ilong = APIClass.mciSendString("close all", TemStr, 128, 0);

　 mc.state = State.mStop ;

}

public void Puase()

{

　 TemStr = "";

　 TemStr = TemStr.PadLeft(128,Convert.ToChar(" "));

　 ilong = APIClass.mciSendString("pause media", TemStr, TemStr.Length, 0);

　 mc.state = State.mPuase ;

}

private string GetCurrPath(string name)

{

　 if(name.Length <1) return "";

　 name = name.Trim();

　 name = name.Substring(0,name.Length-1);

　 return name;

}

//总时间

public int Duration

{

　 get

　 {

durLength = "";

durLength = durLength.PadLeft(128,Convert.ToChar(" ")) ;

APIClass.mciSendString("status media length", durLength, durLength.Length, 0);

durLength = durLength.Trim();

if(durLength == "") return 0;

return (int)(Convert.ToDouble(durLength) / 1000f);

　 }

}

//当前时间

public int CurrentPosition

{

　 get

　 {

durLength = "";

durLength = durLength.PadLeft(128,Convert.ToChar(" ")) ;

APIClass.mciSendString("status media position", durLength, durLength.Length, 0);

mc.iPos = (int)(Convert.ToDouble(durLength) / 1000f);

return mc.iPos;

　 }

}

　 }

　 public class APIClass

　 {

[DllImport("kernel32.dll", CharSet = CharSet.Auto)]

public static extern int GetShortPathName (

　 string lpszLongPath,

　 string shortFile,

　 int cchBuffer

);

[DllImport("winmm.dll", EntryPoint="mciSendString", CharSet = CharSet.Auto)]

public static extern int mciSendString (

　 string lpstrCommand,

　 string lpstrReturnString,

　 int uReturnLength,

　 int hwndCallback

);

　 }

}