Can't write to file using binarywriter

Question

Why does this code not write my string to the file:

 string file = "Myfile.txt";
        MemoryStream ms = new MemoryStream();

void writeToFile(string text)
        {
            System.Text.ASCIIEncoding  encoding=new System.Text.ASCIIEncoding();
            byte[] barr = encoding.GetBytes(text);


            ms.Write(barr, 0, barr.Length);

            using (FileStream fs = new FileStream(file, FileMode.OpenOrCreate))
            {
                using (BinaryWriter bw = new BinaryWriter(ms))
                {
                    bw.Write(ms.ToArray());
                }
            }
        }


        static void Main(string[] args)
        {

            Program p = new Program();

            p.writeToFile("Tony Test");

            Console.ReadLine();

        }

what actually happens? Error, empty file? – H H Jul 15 '10 at 09:26 — H H, Jul 15 '10 at 09:26

score 10 · Accepted Answer · answered Jul 15 '10 at 09:26

10

Look at this line:

using (BinaryWriter bw = new BinaryWriter(ms))

You're writing back to the MemoryStream. You want:

using (BinaryWriter bw = new BinaryWriter(fs))

Having said that, this is a pretty nasty way of writing to a file, with all kinds of unnecessary steps. Hopefully this was just experimentation trying to work out why something else wasn't working - but if your real code is actually like this, please give details of what you're trying to do and we can help you tidy it up.

answered Jul 15 '10 at 09:26

Jon Skeet

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This is copied from a piece of production code, not written by me, that was failing to write to the file and I was attempting to debug it. Could you just tell me what is nasty about it? It really is supposed to take a memorystream and write the contents (a string) to a file... – Tony The Lion Jul 15 '10 at 09:48
This code forces the process to copy all of the contents of the `MemoryStream` (with the`ToArray()` call). See e.g. http://stackoverflow.com/questions/230128/best-way-to-copy-between-two-stream-instances-c for better methods. – Pontus Gagge Jul 15 '10 at 09:51
Thanks, so what does the ToArray call copy more then the method provided in your link? – Tony The Lion Jul 15 '10 at 10:18
@Tony: Use `MemoryStream.WriteTo` to do this in a much nicer fashion... and you don't need a `BinaryWriter` either. The code to populate the memory stream is somewhat wasteful too. – Jon Skeet Jul 15 '10 at 10:29

score 3 · Answer 2 · answered Jul 15 '10 at 09:27

3

You are using the MemoryStream ms for both input and output. Change the line

using (BinaryWriter bw = new BinaryWriter(ms))

to

using (BinaryWriter bw = new BinaryWriter(fs))

answered Jul 15 '10 at 09:27

tafa

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score 0 · Answer 3 · answered Jul 15 '10 at 09:26

0

Alternatively:

File.WriteAllText("myfile", "mytext");

answered Jul 15 '10 at 09:26

Adam Houldsworth

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score 0 · Answer 4 · answered Jul 15 '10 at 10:39

You are writing to text wtih the hardest way possible. you should use File.WriteAllText (as Adam says) or Append text method. If you want to use a writer with special encoding than you should use StreamWriter, since it works with text data and you can set the Encoding of the file.

Can't write to file using binarywriter

4 Answers4