File.ReadAllBytes

This C# method returns a byte array. ReadAllBytes() is simple to call—it receives a file name and returns the file data.

This method can be combined with other types to create high performance file formats. We can use this method to implement an in-memory data representation.

Code example

We see the syntax for calling File.ReadAllBytes. The method returns a byte array, which will be stored in the large object heap if it is large.

using System;
using System.IO;

class Program
{
    static void Main()
    {
        byte[] array = File.ReadAllBytes("C:\\a");
        Console.WriteLine("First byte: {0}", array[0]);
        Console.WriteLine("Last byte: {0}", array[array.Length - 1]);
        Console.WriteLine(array.Length);
    }
}
First byte: 29
Last byte: 0
5407219

Internals

ReadAllBytes() uses the using-statement on a FileStream. Then it loops through the file and puts the bytes into an array. It throws an exception if the file exceeds 2 gigabytes.

Discussion

After using ReadAllBytes, you can use MemoryStream and BinaryReader to read in a binary file you had previously generated with BinaryWriter. This yields fast file formats.

ReadAllBytes loads a binary file into memory. It has a simple calling pattern and is implemented in a straightforward and efficient way.