Create Text File Without BOM

I tried this aproach without any success

the code I'm using:

// File name
String filename = String.Format("{0:ddMMyyHHmm}", dtFileCreated);
String filePath = Path.Combine(Server.MapPath("App_Data"), filename + ".txt");

// Process       
myObject pbs = new myObject();         
pbs.GenerateFile();

// pbs.GeneratedFile is a StringBuilder object

// Save file
Encoding utf8WithoutBom = new UTF8Encoding(true);
TextWriter tw = new StreamWriter(filePath, false, utf8WithoutBom);
foreach (string s in pbs.GeneratedFile.ToArray()) 
    tw.WriteLine(s);
tw.Close();

// Push Generated File into Client
Response.Clear();
Response.ContentType = "application/vnd.text";
Response.AppendHeader("Content-Disposition", "attachment; filename=" + filename + ".txt");
Response.TransmitFile(filePath);
Response.End();

the result:

It's writing the BOM no matter what, and special chars (like Æ Ø Å) are not correct :-/

I'm stuck!

My objective is create a file using UTF-8 as Encoding and 8859-1 as CharSet

Is this so hard to accomplish or I'm just getting a bad day?

All help is greatly appreciated, thank you!

Well it writes the BOM because you are instructing it to, in the line

Encoding utf8WithoutBom = new UTF8Encoding(true);

true means that the BOM should be emitted, using

Encoding utf8WithoutBom = new UTF8Encoding(false);

writes no BOM.

My objective is create a file using UTF-8 as Encoding and 8859-1 as CharSet

Sadly, this is not possible, either you write UTF-8 or not. I.e. as long as the characters you are writing are present in ISO Latin-1 it will look like a ISO 8859-1 file, however as soon as you output a character that is not covered by ISO 8859-1 (e.g. ä,ö, ü) these characters will be written as a multibyte character.

To write true ISO-8859-1 use:

Encoding isoLatin1Encoding = Encoding.GetEncoding("ISO-8859-1");

Edit: After balexandre's comment

I used the following code for testing ...

var filePath = @"c:\temp\test.txt";
var sb = new StringBuilder();
sb.Append("dsfaskd jlsadfj laskjdflasjdf asdkfjalksjdf lkjdsfljas dddd jflasjdflkjasdlfkjasldfl asääääjdflkaslj d f");

Encoding isoLatin1Encoding = Encoding.GetEncoding("ISO-8859-1");

TextWriter tw = new StreamWriter(filePath, false, isoLatin1Encoding);
tw.WriteLine(sb.ToString());
tw.Close();

And the file looks perfectly well. Obviously, you should use the same encoding when reading the file.