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);
}

1

Thanks! 👍

@dojo90 @milovidov983 What's the point of the convert? as the str and str2 are the same string after the convert

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

@dojo90 @milovidov983 What's the point of the convert? as the str and str2 are the same string after the convert

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

1. At the time when I wrote this function, it seemed to me that it solved my problem and the resulting CSV file immediately recognized the correct cyrillic encoding when opened by Excel.

2. By the way it looks like the strings are not equivalent. Or am I wrong?:
   https://dotnetfiddle.net/mYgvdl

Example

using System;
using System.Text;
using System.Linq;
public class Program {
	public static void Main() {
		var str = "aîn";
		var str2 = ConvertStringToUtf8Bom(str);
		Console.WriteLine(str2);

		Console.WriteLine(str == str2);

		var str3 = "aîn";
		Console.WriteLine(str == str3);
	}
	static 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);
	}

}

// Output:
/*
aîn
False
True
*/

@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!