C# - How do I read and write a binary file?

Question

How do I read a raw byte array from any file, and write that byte array back into a new file?

Encoding & BinaryWriter? Encoding is a "string" thingy. You shouldn't have a problem when you are dealing with binary data. — Mehrdad Afshari, Sep 20 '09 at 07:49
Jeremy, do you mean "depending on the file type the *format* varies..." ? if the code you're using tries to read/write files with the wrong file type/format I'm sure there would be corruption. — pavium, Sep 20 '09 at 07:58
Reading a file as a `byte[]` is not necessarily a good idea; this could be **very** expensive for large files. — Marc Gravell, Sep 20 '09 at 08:23

score 7 · Accepted Answer · edited May 23 '17 at 12:29

(edit: note that the question changed; it didn't mention byte[] initially; see revision 1)

Well, File.Copy leaps to mind; but otherwise this sounds like a Stream scenario:

    using (Stream source = File.OpenRead(inPath))
    using (Stream dest = File.Create(outPath)) {
        byte[] buffer = new byte[2048]; // pick size
        int bytesRead;
        while((bytesRead = source.Read(buffer, 0, buffer.Length)) > 0) {
            dest.Write(buffer, 0, bytesRead);
        }
    }

score 5 · Answer 2 · answered Sep 20 '09 at 08:07

5

byte[] data = File.ReadAllBytes(path1);
File.WriteAllBytes(path2, data);

answered Sep 20 '09 at 08:07

Tommy Carlier

7,951
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2

Note that for large files that could be *very* expensive. – Marc Gravell Sep 20 '09 at 08:20

score 3 · Answer 3 · answered Sep 20 '09 at 07:59

3

Do you know about TextReader and TextWriter, and their descendents StreamReader and StreamWriter? I think these will solve your problem because they handle encodings, BinaryReader does not know about encodings or even text, it is only concerned with bytes.

How to read text from a file

How to write text to a file

This is an excellent intro to file IO and encodings.

answered Sep 20 '09 at 07:59

Dale

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Jeremy asked about reading and writing BINARY files, didn't he? – pavium Sep 20 '09 at 08:02
3

If it is just binary data, then why is there any problem with the char encoding? – Dale Sep 20 '09 at 08:09

score 0 · Answer 4 · answered Jun 21 '13 at 08:13

Adding an up to date answer,

using (var source = File.OpenRead(inPath))
{
    using (var dest = File.Create(outPath))
    {
        source.CopyTo(dest);
    }
}

you can optionally specify the buffer size

using (var source = File.OpenRead(inPath))
{
    using (var dest = File.Create(outPath))
    {
        source.CopyTo(dest, 2048); // or something bigger.
    }
}

or you could perform the operation on another thread,

using (var source = File.OpenRead(inPath))
{
    using (var dest = File.Create(outPath))
    {
        await source.CopyToAsync(dest);
    }
}

which would be useful when the main thread has to do other work, like with WPF and Windows Store apps.

C# - How do I read and write a binary file?

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