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
{