How to output Byte Order Mark when writing to TextWriter?

Short Version

String zwnbsp = "\xfeff"; //Zero-width non-breaking space

//The Zero-width non-breaking space character ***is*** the Byte-Order-Mark (BOM).
String s = zwnbsp+"The quick brown fox jumped over the lazy dog.";
writer.Write(s);

Long Version

At some point i realized how simple the solution is.

i used to think that the Unicode Byte-Order-Mark was some special signature. i used to think i had to carefully decide which byte sequence i wanted to output, in order to output the correct BOM:

• 0xFE 0xFF
• 0xFF 0xFE
• 0xEF 0xBB 0xBF

But since then i realized that byte Byte-Order-Mark is not some special byte sequence that you have to prepend to your file.

The BOM is just a Unicode character. You don't output any bytes; you only output character U+FEFF. The very act of writing that character, the serializer will convert it to whatever encoding you're using for you.

The character U+feff (ZERO WIDTH NO-BREAK SPACE) was chosen for good reason. It's a space, so it has no meaning, and it is zero width, so you shouldn't even see it.

That means that my question is fundamentally flawed. There is no such thing as "writing a byte-order-mark". You just make sure the first character you write out is U+FEFF. In my case i am writing to a TextWriter:

void WriteStuffToTextWriter(TextWriter writer)
{
   String csvExport = GetExportAsCSV();

   writer.Write("\xfeff"); //Output unicode charcter U+FEFF as a byte order marker
   writer.Write(csvExport);
}

The TextWriter will handle converting the unicode character U+feff into whatever byte encoding it has been configured to use.

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