(.NET)How to convert string to bytes array that is encoded UTF-8 with BOM.

StringExtension.cs

using System.IO;
namespace Sample
{
  public static class EncodingExtension
  {
        public static byte[] GetUtf8WithBomBytes(this string str)
        {
            var encoding = new UTF8Encoding(true)
            using (var stream = new MemoryStream())
            using (var writer = new StreamWriter(stream, encoding))
            {
                writer.Write(str);
                var bytes = stream.ToArray();
                return encoding.GetPreamble().Concat(bytes).ToArray();
            }
        }
    }
}

using System.Text; とかも必要だけど察して

https://stackoverflow.com/questions/4414088/how-to-getbytes-in-c-sharp-with-utf8-encoding-with-bom
https://codeday.me/jp/qa/20190107/108132.html
https://smdn.jp/programming/netfx/tips/unicode_encoding_bom/
参考にしてたページ