PM> Install-Package NAudio

使用NAudio.Wave添加;并使用此代码：

void Main()
{
     var mp3Path = @"C:\Users\Ronnie\Desktop\podcasts\hanselminutes_0350.mp3";  
     var outputPath = Path.ChangeExtension(mp3Path,".trimmed.mp3");

     TrimMp3(mp3Path,outputPath,TimeSpan.FromMinutes(2),TimeSpan.FromMinutes(2.5));
}

void TrimMp3(string inputPath,string outputPath,TimeSpan? begin,TimeSpan? end)
{
    if (begin.HasValue && end.HasValue && begin > end)
        throw new ArgumentOutOfRangeException("end","end should be greater than begin");

    using (var reader = new Mp3FileReader(inputPath))
    using (var writer = File.Create(outputPath))
    {           
        Mp3Frame frame;
        while ((frame = reader.ReadNextFrame()) != null)
        if (reader.CurrentTime >= begin || !begin.HasValue)
        {
            if (reader.CurrentTime <= end || !end.HasValue)
                writer.Write(frame.RawData,frame.RawData.Length);         
            else break;
        }
    }
}

快乐的小道.