SendGrid.Net.Mime.ContentType.To2047 C# (CSharp) Method

        internal static string To2047(byte[] bytes)
        {
            var sb = new StringBuilder();
            foreach (byte i in bytes)
            {
                if (i < 0x21 || i > 0x7E || i == '?' || i == '=' || i == '_')
                {
                    sb.Append('=');
                    sb.Append(hex[(i >> 4) & 0x0f]);
                    sb.Append(hex[i & 0x0f]);
                }
                else
                    sb.Append((char)i);
            }
            return sb.ToString();
        }