DLL To Decode MP3 To WAV/PCM

 public partial class Form1 : Form
    {
        [MarshalAs(UnmanagedType.LPStr)] private StringBuilder strBuilder = new StringBuilder("",11000);
        MadlldlibWrapper.Callback updateFunction ;
        string mp3File = "";
        string wavFile = "";
        Boolean bCancel = false;
        OpenFileDialog Dialog = new OpenFileDialog();
        
        public Form1()
        {
            InitializeComponent();
            updateFunction  = new MadlldlibWrapper.Callback(updateFunctionMethod);
        }
        
        private Boolean updateFunctionMethod(uint frameCount, uint byteCount,ref Mp3Decoder.MadlldlibWrapper.mad_header madHeader)
        {
            if (frameCount == 1)
            {
                this.label1.Text = "Sampelrate: " + madHeader.samplerate.ToString() + 
                    " Bitrate: " + madHeader.bitrate.ToString() + 
                    " Duration: " + madHeader.duration + 
                    " Layer: " + madHeader.layer.ToString();
                Application.DoEvents();
            }
            this.label3.Text = "frame:= " + frameCount.ToString() + " byte:= " + byteCount.ToString();
            Application.DoEvents();
            if (bCancel) {
                return false;
                }
            else { return true; }
        }
 

        private void selectMp3ToolStripMenuItem1_Click(object sender, EventArgs e)
        {
            Dialog.Filter = "mp3 files (*.mp3)|*.mp3";
            Dialog.Multiselect = false;
            Dialog.ShowDialog();
            if (Dialog.FileName != "") {
                this.label3.Text = "";
                mp3File = Dialog.FileName;
                this.textBox1.Text = Dialog.FileName;
                wavFile = Dialog.FileName.Remove(Dialog.FileName.LastIndexOf("."), Dialog.FileName.Length - Dialog.FileName.LastIndexOf(".")) + ".wav";
            } 
        }
 
        private void exitToolStripMenuItem_Click(object sender, EventArgs e)
        {
            this.Close();
        }
 
        private void button1_Click(object sender, EventArgs e)
        {
            MadlldlibWrapper.DecodeMP3(mp3File, wavFile, 1, strBuilder, updateFunction);
            this.label3.Text = "Conversion done!";
        }
 
        private void button2_Click(object sender, EventArgs e)
        {
            this.bCancel = true;
        }
    }

namespace Mp3Decoder
{
	using System;
	using System.Text;	
	using System.Runtime.InteropServices;
 
	// Alias; see SF_INFO struct:

	using sf_count_t = System.Int64;	
 
	
#if PLATFORM_64
	using size_t = System.UInt64;
#else
	using size_t = System.UInt32;
#endif
	
 
	class MadlldlibWrapper
	{
 

		// Type declarations hence

		public enum mad_layer : int 
		{
			MAD_LAYER_I   = 1,          // Layer I 
			MAD_LAYER_II  = 2,          // Layer II 
			MAD_LAYER_III = 3           // Layer III 
		};
 
		
		public enum mad_mode : int 
		{
			MAD_MODE_SINGLE_CHANNEL = 0,      // Single channel 
			MAD_MODE_DUAL_CHANNEL   = 1,      // Dual channel 
			MAD_MODE_JOINT_STEREO   = 2,      // Joint (MS/intensity) stereo 
			MAD_MODE_STEREO         = 3       // Normal LR stereo 
		};
		
 
		public enum mad_emphasis : int 
		{
			MAD_EMPHASIS_NONE	      = 0,        // No emphasis 
			MAD_EMPHASIS_50_15_US	  = 1,        // 50/15 microsecs emphasis 
			MAD_EMPHASIS_CCITT_J_17   = 3,        // CCITT J.17 emphasis 
			MAD_EMPHASIS_RESERVED     = 2         // Unknown emphasis 
		};
 

		public struct mad_timer_t 
		{
		  long seconds;     // Whole seconds 
		  uint fraction;    // 1/MAD_TIMER_RESOLUTION seconds 
		};
		
 
		[StructLayout(LayoutKind.Sequential), Serializable]	
		public struct mad_header 
		{
			public mad_layer layer;             // Audio layer (1, 2, or 3) 
			public mad_mode mode;               // Channel mode 
			public int mode_extension;          // Additional mode info 
			public mad_emphasis emphasis;       // De-emphasis to use

			public uint bitrate;                // Stream bitrate (bps) 
			public uint samplerate;             // Sampling frequency (Hz) 

			public ushort crc_check;            // Frame CRC accumulator 
			public ushort crc_target;           // Final target CRC checksum 

			public int flags;                   // Flags 
			public int private_bits;            // Private bits 

			public mad_timer_t duration;        // Audio playing time of frame 
		};
 

		// Decoding flags

		public const int DEC_WAV = 1;
		public const int DEC_PCM = 0;
 

 
		// Method declarations hence		
		
		
		
		// Callback function is used to pass values
		// related to the decoding process back to
		// the calling code. Use return value to 
		// cancel conversion (set to false)

		public delegate bool 
		Callback( uint frameCount,  uint byteCount, 
				ref mad_header madHeader);	
		
		
		// Conversion routine referencing callback--
		// see madlldlib.cpp source for details about 
		// this function

		[DllImport("madlldlib.dll",	EntryPoint = "CbMpegAudioDecoder")]
		public static extern int 
		DecodeMP3(
				string inFile,
				string outFile,
				int decodeType,				// WAV or PCM
				// Marshalled status message:
				[MarshalAs(UnmanagedType.LPStr)] StringBuilder statmsg,
				Callback updateFunction			// Callback function
				);
	
 
	} 
 
	
}