public byte[] GetCsv()
{
    var stream = new MemoryStream();
    var csvWriter = new StreamWriter(stream, Encoding.GetEncoding("shift-jis"));
    csvWriter.WriteLine(String.Format("{0},{1},{2},{3}", "aaa", "bbb", "ccc", "ddd"));
    csvWriter.Flush();
            
    return stream.ToArray();
}