Best way to read a large file into a byte array in C#?

Question

I have a web server which will read large binary files (several megabytes) into byte arrays. The server could be reading several files at the same time (different page requests), so I am looking for the most optimized way for doing this without taxing the CPU too much. Is the code below good enough?

public byte[] FileToByteArray(string fileName) {     byte[] buff = null;     FileStream fs = new FileStream(fileName,                                     FileMode.Open,                                     FileAccess.Read);     BinaryReader br = new BinaryReader(fs);     long numBytes = new FileInfo(fileName).Length;     buff = br.ReadBytes((int) numBytes);     return buff; } 

Answer 1

Simply replace the whole thing with:

return File.ReadAllBytes(fileName); 

However, if you are concerned about the memory consumption, you should not read the whole file into memory all at once at all. You should do that in chunks.

Answer 2

I might argue that the answer here generally is "don't". Unless you absolutely need all the data at once, consider using a Stream-based API (or some variant of reader / iterator). That is especially important when you have multiple parallel operations (as suggested by the question) to minimise system load and maximise throughput.

For example, if you are streaming data to a caller:

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