C# MP3 Player using winmm.dll

I'm trying to bash together a (very) rough MP3 player during my lunch hour, and so far I've got it to play the files, and I'm working on a way of building a list of filenames to enable random songs, but I think I've just hit a snag.

Is there a way of knowing when the currently playing MP3 has finished? An event or some such? As it stands I don't think I'd be able to have playlists etc unless this was possible due to it stopping after every playback.

I've attatched the whole source below, feel free to pick it apart and give me any feedback you may have, cheers.

using System;
using System.IO;
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 X
{
public partial class Form1 : Form
{
    List<string> Names = new List<string>();
    StreamReader reader = File.OpenText(@"C:\X.txt");
    string line;
    OpenFileDialog ofd = new OpenFileDialog();
    StringBuilder buffer = new StringBuilder(128);
    string CommandString;
    [DllImport("winmm.dll")]
    private static extern long mciSendString(string lpstrCommand, StringBuilder lpstrReturnString, int uReturnLength, int hwndCallback);
    public Form1()
    {
        InitializeComponent();
        while ((line = reader.ReadLine()) != null)
        {
            if (line.Trim() != "")
            {
                Names.Add(line.Trim());
            }
        }
    }

    private void btnplay_Click(object sender, EventArgs e)
    {
        if (ofd.FileName == "")
        {
            if (ofd.ShowDialog() == DialogResult.OK)
            {
                ofd.Filter = "MP3 Files|*.mp3";
                CommandString = "open " + "\"" + ofd.FileName + "\"" + " type MPEGVideo alias Mp3File";
                mciSendString(CommandString, null, 0, 0);
                CommandString = "play Mp3File";
                mciSendString(CommandString, null, 0, 0);
            }
        }

        else
        {
            CommandString = "play Mp3File";
            mciSendString(CommandString, null, 0, 0);
        }
    }

    private void btnpause_Click(object sender, EventArgs e)
    {
        CommandString = "pause mp3file";
        mciSendString(CommandString, null, 0, 0);
    }

    private void btnbrowse_Click(object sender, EventArgs e)
    {
        ofd.Filter = "Mp3 files |*.mp3";
        if (ofd.ShowDialog() == DialogResult.OK)
        {
            txtpath.Text = ofd.FileName;
            CommandString = "close Mp3File";
            mciSendString(CommandString, null, 0, 0);
            CommandString = "open " + "\"" + ofd.FileName + "\"" + " type MPEGVideo alias Mp3File";
            mciSendString(CommandString, null, 0, 0);
        }
    }
}
}

You can get notification from mcisendstring command when you calling mcisendstring for opening the file just send the handle of your form and override the wndproc method of your form then u can get the notify from MCI sample code as follow.`

 private void btnplay_Click(object sender, EventArgs e)
{
    if (ofd.FileName == "")
    {
        if (ofd.ShowDialog() == DialogResult.OK)
        {
            ofd.Filter = "MP3 Files|*.mp3";
            CommandString = "open " + "\"" + ofd.FileName + "\"" + " type MPEGVideo alias Mp3File";
            mciSendString(CommandString, null, 0, this.Handle.ToInt64());
            CommandString = "play Mp3File";
            mciSendString(CommandString, null, 0, this.Handle.ToInt64());
        }
    }

    else
    {
        CommandString = "play Mp3File";
        mciSendString(CommandString, null, 0, this.Handle.ToInt64());
    }
}

// Declare the nofify constant
public const int MM_MCINOTIFY = 953;

// Override the WndProc function in the form
protected override void WndProc(ref Message m) 
{

    if (m.Msg == MM_MCINOTIFY)
    {
        // The file is done playing, do whatever
    }
    base.WndProc(ref m);
}