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?

Answer 1

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

Answer 2

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.

Answer 3

(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);
        }
    }

Answer 4

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.