c# - Add byte order mark to a string via StringBuilder -

how can add byte order mark stringbuilder? (i have pass string method save file, can't modify method).

i tried this:

var sb = new stringbuilder(); sb.append('\xef'); sb.append('\xbb'); sb.append('\xbf'); 

but when view hex editor, adds following sequence: c3 af c2 bb c2 bf

the string huge, without , forth converting byte array.

edit: clarification after questions in comments. have pass string method takes string , creates file of on azure blob storage. can't modify other method.

two options:

1. don't include byte order mark in text @ all... instead use encoding automatically include it

2. include as character in stringbuilder:

   sb.append('\ufeff'); // u+feff byte-order mark character 

personally i'd go first approach normally, "i can't modify method" suggests may not option in case.