照书上抄了一个小simplemp3player,可是怎么也不会响，大家帮忙看看，是怎么回事

Question

     using System;using System.Collections.Generic;using System.ComponentModel;using System.Data;using System.Drawing;using System.Linq;using System.Text;using System.Windows.Forms;using System.Runtime.InteropServices;namespace simpleMP3Player{ public partial class form1 : Form { public form1() { InitializeComponent(); } [DllImport("winmm.dll", EntryPoint = "mciSendString", CharSet = CharSet.Auto)] private static extern long mciSendString(string lpstrCommand, StringBuilder lpsstrReturnString, int uReturnLength, int hwndCallback); private string sFileName; StringBuilder buffer = new StringBuilder(128); private void form1_Load(object sender, EventArgs e) { btnPlay.Enabled = false; btnPause.Enabled = false; btnPre.Enabled = false; btnStop.Enabled = false; btnNext.Enabled = false; timer.Enabled = false; timer.Interval = 500; } private void btnOpen_Click(object sender, EventArgs e) { if (openFileDialog.ShowDialog(this) == DialogResult.OK) { if (sFileName != null && sFileName.Trim() != "") { mciSendString("stop MP3File", null, 0, 0); mciSendString("close MP3File", null, 0, 0); } sFileName = openFileDialog.FileName; string strLength = ""; buffer = new StringBuilder(128); mciSendString("open \""+ sFileName +"\""+" type MPEGVideo alias MP3File", null, 0, 0); mciSendString("set MP3File time format milliseconds", null, 0, 0); mciSendString("set MP3File seek exactly on", null, 128, 0); mciSendString("seek MP3File to start", null, 0, 0); mciSendString("status MP3File length",buffer, 128, 0); strLength = buffer.ToString().PadLeft(8,' ').Substring (0,8); if (strLength .Trim() !="") { progressBar.Minimum =0; progressBar .Value=0; progressBar.Maximum =int.Parse (strLength ); } TimeSpan ts = new TimeSpan(long.Parse(strLength) * 10000); lbCurrent.Text="00:00:00"; lbBegin.Text="00:00:00"; toolStripStatusLabel1 .Text=""; lbEnd.Text=ts.Hours.ToString("00:")+ts.Minutes.ToString("00:")+ts.Seconds .ToString("00"); timer.Enabled = false; btnPlay.Enabled=true; } } private void btnPlay_Click(object sender, EventArgs e) { string strMode = ""; btnPause.Enabled = true; btnStop.Enabled = true; btnPre.Enabled = true; btnNext.Enabled = true; mciSendString("play MP3File from" + progressBar.Value.ToString(), null, 0, 0); mciSendString("status MP3File mode", buffer, 128, 0); strMode = buffer.ToString().PadLeft(8, ' ').Substring(0, 8); toolStripStatusLabel1.Text = strMode; timer.Enabled = true; } private void btnPause_Click(object sender, EventArgs e) { mciSendString("pause MP3File", null, 0, 0); btnPlay.Enabled = true; btnPause.Enabled = false; btnStop.Enabled = false; btnPre.Enabled = false; btnNext.Enabled = false; } private void btnStop_Click(object sender, EventArgs e) { mciSendString("seek MP3File to start",null,0,0); mciSendString("stop MP3File", null, 0, 0); btnPlay.Enabled = true; btnPause.Enabled = false; btnStop.Enabled = false; btnPre.Enabled =false ; btnNext.Enabled = false; } private void btnPre_Click(object sender, EventArgs e) { mciSendString("play MP3File from" + ((int)(progressBar.Value -(progressBar.Maximum / 10))).ToString(), null, 0, 0); } private void btnNext_Click(object sender, EventArgs e) { mciSendString("play MP3File from" + ((int)(progressBar.Value + (progressBar.Maximum / 10))).ToString(), null, 0, 0); } private void timer_Tick(object sender, EventArgs e) { string strPosition = ""; string strMode = ""; buffer = new StringBuilder(128); mciSendString("status MP3File position", buffer, 128, 0); if (buffer.Length >= 8) { strPosition = buffer.ToString(0, 8); } else { strPosition = buffer.ToString(); } progressBar.Value = int.Parse(strPosition); TimeSpan ts = new TimeSpan(long.Parse(strPosition) * 10000); lbCurrent.Text = ts.Hours.ToString("00:") + ts.Minutes.ToString("00:") + ts.Seconds.ToString("00"); if (progressBar.Value == progressBar.Maximum) { btnStop_Click(null,null); } buffer = new StringBuilder(128); mciSendString("status MP3File mode", buffer, 128, 0); strMode = buffer.ToString().PadLeft(8, ' ').Substring(0, 8); toolStripStatusLabel1.Text = strMode; } private void form1_FormClosing(object sender, FormClosingEventArgs e) { mciSendString("close MP3File", null, 0, 0); } }}