Determine File Encoding

[Marc Jennings]

Hi there,

Can anyone point out any really obvious flaws in the methodology below
to determine the likely encoding of a file, please? I know the number
of types of encoding is small, but that is only because the
possibilities I need to work with is a small list.

private string determineFileEn coding(FileStre am strm)
{
long originalSize = strm.Length;
StreamReader rdr = new StreamReader(st rm);

strm.Position = 0;
System.Text.UTF 8Encoding unic = new System.Text.UTF 8Encoding();
byte[] inputFile = unic.GetBytes(r dr.ReadToEnd()) ;
if(inputFile.Le ngth == originalSize)
{
return "UTF8";
}

strm.Position = 0;
System.Text.Uni codeEncoding unic2 = new System.Text.Uni codeEncoding();
byte[] inputFile2 = unic2.GetBytes( rdr.ReadToEnd() );
if(inputFile2.L ength == originalSize)
{
return "Unicode";
}

strm.Position = 0;
System.Text.UTF 7Encoding unic3 = new System.Text.UTF 7Encoding();
byte[] inputFile3 = unic3.GetBytes( rdr.ReadToEnd() );
if(inputFile3.L ength == originalSize)
{
return "UTF7";
}

System.Text.ASC IIEncoding unic4 = new System.Text.ASC IIEncoding();
byte[] inputFile4 = unic3.GetBytes( rdr.ReadToEnd() );
if(inputFile4.L ength == originalSize)
{
return "Ascii";
}

return "Not known";
}

Thanks in advance
Marc.

[Jon Skeet [C# MVP]]

Roby Eisenbraun Martins
<Ro************ *******@discuss ions.microsoft. com> wrote:

If you open a file using StreamReader it will load a CurrentEncoding
with the correct file encoding and convert the bytes to the correct
characters.

Only if you're lucky. It won't be able to guess correctly between
different ANSI character sets, for instance.

It's definitely best to take the guesswork out, either by explicitly
stating the encoding, making sure there *is* only one encoding, or
allowing the user to override any guesswork which has been performed.

--
Jon Skeet - <sk***@pobox.co m>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too