How to convert UTF-8 to UTF-8 with BOM c# string

ConvertStringToUtf8Bom.cs

private string ConvertStringToUtf8Bom(string source) {
  var data = Encoding.UTF8.GetBytes(source);
  var result = Encoding.UTF8.GetPreamble().Concat(data).ToArray();
  var encoder = new UTF8Encoding(true);

  return encoder.GetString(result);
}

@milovidov983，Thanks, I tried to print the bytes array, it make sense.

  var str = "aîn";
            var str2 = ConvertStringToUtf8Bom(str);
            Console.WriteLine(str2 == str);

            Console.WriteLine($"length of {str} is {str.Length}");
            var bytes1 = Encoding.UTF8.GetBytes(str);
            Console.WriteLine(GetHexString(bytes1));

            Console.WriteLine();

            Console.WriteLine($"length of {str2} is {str2.Length}");
            var bytes2 = Encoding.UTF8.GetBytes(str2);
            Console.WriteLine(GetHexString(bytes2));

False
length of aîn is 3
61 C3 AE 6E

length of aîn is 4
EF BB BF 61 C3 AE 6E

By the way, I am using stream writer to create a new file with Encoding.UTF8, and it will handle the BOM automatically.
https://github.com/dotnet/runtime/blob/6ef4b2e7aba70c514d85c2b43eac1616216bea55/src/libraries/System.Private.CoreLib/src/System/IO/StreamWriter.cs#L273

does the above code add Carriage return when processing ?

Thanks guys! This helped!