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I have a byte array which I got back from a FileStream.Read and I would like to turn that into a string. I'm not 100% sure of the encoding - it's just a file i saved to disk - how do I do the conversion? Is there a .NET class that reads the byte order mark and can figure out the encoding for me?

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6 Answers 6

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See how-to-guess-the-encoding-of-a-file-with-no-bom-in-net.

Since strings are Unicode, you must specify an encoding on conversion. Text streams (even ReadAllText() ) have an active encoding inside, usually some sensible default.

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Try something like this:

buffer = Encoding.Convert( Encoding.GetEncoding("iso-8859-1"), Encoding.UTF8, buffer );
newString = Encoding.UTF8.GetString( buffer, 0, len );
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Why would that be better than just using Encoding.GetEncoding("iso-8859-1").GetString(...) in the first place? The point is that the OP doesn't know what the encoding is.
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If File.ReadAllText will read the file correctly, then you have a couple of options.

Instead of calling BeginRead, you could just call File.ReadAllText asynchronously:

    delegate string AsyncMethodCaller(string fname);

    static void Main(string[] args)
    {
        string InputFilename = "testo.txt";
        AsyncMethodCaller caller = File.ReadAllText;
        IAsyncResult rslt = caller.BeginInvoke(InputFilename, null, null);

        // do other work ...

        string fileContents = caller.EndInvoke(rslt);
    }

Or you can create a MemoryStream from the byte array, and then use a StreamReader on that.

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How much do you know about the file? Could it really be any encoding? If so, you'd need to use heuristics to guess the encoding. If it's going to be UTF-8, UTF-16 or UTF-32 then 

new StreamReader(new MemoryStream(bytes), true)

will detect the encoding for you automatically. Text is pretty nasty if you really don't know the encoding though. There are plenty of cases where you really would just be guessing.

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There is no simple way to get the encoding, but as mentioned above use 

string str = System.Text.Encoding.Default.GetString(mybytearray);

if you have no clue of what the encoding is. If you are in europe the ISO-8859-1 is probably the encoding you have.

string str = System.Text.Encoding.GetEncoding("ISO-8859-1").GetString(mybytearray);
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System.IO.File.ReadAllText does what you want.

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4 Comments

I would if I could, but unfortunately I need to do this async using the BeginRead method which only returns a byte array...
Fair enough then. In which case, jon skeet's answer below (or above, now, probably) is good.
Also ReadAllText assumes UTF-8.
MSDN for readalltext states it auto-detects: "This method attempts to automatically detect the encoding of a file based on the presence of byte order marks. Encoding formats UTF-8 and UTF-32 (both big-endian and little-endian) can be detected."

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