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);
        }
        
    }
}