Trim a wav file

Question

I'm trying to trim a file using the code from here

 public static void TrimWavFile(string inPath, string outPath, TimeSpan cutFromStart, TimeSpan cutFromEnd)
 {
    using (WaveFileReader reader = new WaveFileReader(inPath))
    {
        using (WaveFileWriter writer = new WaveFileWriter(outPath, reader.WaveFormat))
        {
            int bytesPerMillisecond = reader.WaveFormat.AverageBytesPerSecond / 1000;

            int startPos = (int)cutFromStart.TotalMilliseconds * bytesPerMillisecond;
            startPos = startPos - startPos % reader.WaveFormat.BlockAlign;

            int endBytes = (int)cutFromEnd.TotalMilliseconds * bytesPerMillisecond;
            endBytes = endBytes - endBytes % reader.WaveFormat.BlockAlign;
            int endPos = (int)reader.Length - endBytes; 

            TrimWavFile(reader, writer, startPos, endPos);
        }
    }
}

private static void TrimWavFile(WaveFileReader reader, WaveFileWriter writer, int startPos, int endPos)
{
    reader.Position = startPos;
    byte[] buffer = new byte[1024];
    while (reader.Position < endPos)
    {
        int bytesRequired = (int)(endPos - reader.Position);
        if (bytesRequired > 0)
        {
            int bytesToRead = Math.Min(bytesRequired, buffer.Length);
            int bytesRead = reader.Read(buffer, 0, bytesToRead);
            if (bytesRead > 0)
            {
                writer.WriteData(buffer, 0, bytesRead);
            }
        }
    }
}

I wrote exactly whats in there but when I'm opening the file i trimmed it says he's corrupted.

How does this code works? The while (reader.Position < endPos) is always true and the reader.Position doesn't change.

Edit 1 The else if() are same as the else but i put it just to be sure.

while (reader.Position < end)
        {
            int bytesRequired = (int)(end - reader.Position);
            if (bytesRequired > 0)
            {
                int bytesToRead = Math.Min(bytesRequired, buffer.Length);
                int bytesRead = reader.Read(buffer, 0, bytesToRead);
                if (bytesRead > 0)
                {
                    writer.Write(buffer, 0, bytesRead);
                }
                else if (bytesRead == 0)
                {
                   break;
                }
            }
            else if (bytesRequired <= 0)
            {
                break;
            }
        }

Answer 1

you should break out of the while loop if bytesRequired <= 0 or if bytesRead == 0