I am not really sure about your implementation of winmm.dll but I have a tested and working code for it.
I got the source code from this open source project: Tea Timer.
The implementation of the code is pretty straight forward as below. Hope it helps.
using System;
using System.Text;
using System.Runtime.InteropServices;
using System.IO;
namespace TeaTimer
{
/// <summary>
/// MCIPlayer is based off code by Slain.
/// Found here: http://www.sadeveloper.net/Articles_View.aspx?articleID=212
/// </summary>
public class MCIPlayer
{
private static readonly string sAlias="TeaTimerAudio";
[DllImport("winmm.dll")]
private static extern long mciSendString(string strCommand,StringBuilder strReturn,int iReturnLength, IntPtr hwndCallback);
[DllImport("Winmm.dll")]
private static extern long PlaySound(byte[] data, IntPtr hMod, UInt32 dwFlags);
public static void Play(string sFile)
{
_Open(sFile);
_Play();
}
public static void Stop()
{
_Close();
}
private static void _Open(string sFileName)
{
if(_Status()!="")
_Close();
string sCommand = "open \"" + sFileName + "\" alias "+sAlias;
mciSendString(sCommand, null, 0, IntPtr.Zero);
}
private static void _Close()
{
string sCommand = "close "+sAlias;
mciSendString(sCommand, null, 0, IntPtr.Zero);
}
private static void _Play()
{
string sCommand = "play "+sAlias;
mciSendString(sCommand, null, 0, IntPtr.Zero);
}
private static string _Status()
{
StringBuilder sBuffer = new StringBuilder(128);
mciSendString("status "+sAlias+" mode", sBuffer, sBuffer.Capacity, IntPtr.Zero);
return sBuffer.ToString();
}
}
}
EDIT: This is how you play and stop a music file:
public static void playSound(string sFile)
{
//WavPlay.WavPlayer.Play(sFile);
MCIPlayer.Play(sFile);
}
public static void stopSound()
{
//WavPlay.WavPlayer.StopPlay();
MCIPlayer.Stop();
}