C# - byte Array Example - Dot Net Perls

Byte array. A byte array can store binary data in C# programs. This data may be part of a data file, image file, compressed file or downloaded server response.

With byte arrays, we have an ideal representation of this data. The byte array type allows us to store low-level representations. It is useful in optimization.

byte, sbyte

Array

Display example. To begin, we create a small byte array in a C# program. Byte arrays can represent any values, but each individual byte can only hold a certain range.

Part 1 We create a byte array of 3 bytes. We store the minimum byte value, and the maximum byte value, in the array elements.

Part 2 We use a foreach-loop to display all the byte elements in the byte array.

foreach

using System; // Part 1: create byte array. byte[] data = new byte[3]; data[0] = byte.MinValue; data[1] = 0; data[2] = byte.MaxValue; // Part 2: display byte data. foreach (var element in data) { Console.WriteLine(element); }

0 0 255

Memory example. Here we allocate a byte array on the managed heap. The program measures the memory usage of the managed heap before and after this allocation occurs.

Detail The GC.GetTotalMemory method gathers the memory usage figures from the system before and after the allocation of the byte array.

GC.Collect

Then The byte array variable is assigned a reference to 3 million bytes in an array allocated on the managed heap.

Result Allocating a 3 million element array of bytes causes 3 million bytes to be added to the memory usage of the program.

ValueType

Tip Here we find that a byte array is a precise representation of bytes, not a higher-level construct.

using System; byte[] array1 = null; // // Allocate three million bytes and measure memory usage. // long bytes1 = GC.GetTotalMemory(false); array1 = new byte[1000 * 1000 * 3]; array1[0] = 0; long bytes2 = GC.GetTotalMemory(false); Console.WriteLine(bytes2 - bytes1);

3000032

Read bytes. We read in a byte array from a file with the System.IO namespace. An easy way to read a file into a binary array is the File.ReadAllBytes method in the File class.

File.ReadAllBytes

using System; using System.IO; class Program { static void Main() { byte[] array = File.ReadAllBytes("C:\\profiles\\file.bin"); Console.WriteLine(array[0]); Console.WriteLine(array[1]); Console.WriteLine(array[2]); } }

56 66 80

ToBase64String. When we have a byte array, we do not just need to leave the data as a byte array. We can convert it to a string with ToBase64String.

Here We load a JPG image on the disk into a byte array, and then encode it as a string. This can be put in CSS or HTML files directly.

ToBase64String

using System; using System.IO; class Program { static void Main() { byte[] data = File.ReadAllBytes(@"C:\perls\i\2d-adventurers-map-background.jpg"); // Get base 64. string result = Convert.ToBase64String(data); // Write first 20 chars. Console.WriteLine("BASE64: " + result.Substring(0, 20) + "..."); } }

BASE64: /9j/2wCEAAgGBgYGBggG...

Test byte array. A GZIP file must have certain bytes in its first few bytes. We use IsGZipHeader to test a byte array to see if it contains GZIP data.

Note The first part of Main reads in a GZIP file, "2About.gz". The result value from IsGZipHeader on this file is true.

Note 2 GZipTool is a public static class, which means you can access it from other namespaces and files. It contains IsGZipHeader.

Info IsGZipHeader returns true if the byte data passed to it contains the values 31 and 139 in its first two bytes.

using System; using System.IO; class Program { static void Main() { byte[] gzip = File.ReadAllBytes("2About.gz"); Console.WriteLine(GZipTool.IsGZipHeader(gzip)); byte[] text = File.ReadAllBytes("Program.cs"); Console.WriteLine(GZipTool.IsGZipHeader(text)); } } /// <summary> /// GZIP utility methods. /// </summary> public static class GZipTool { /// <summary> /// Checks the first two bytes in a GZIP file, which must be 31 and 139. /// </summary> public static bool IsGZipHeader(byte[] arr) { return arr.Length >= 2 && arr[0] == 31 && arr[1] == 139; } }

True False

In C# programs we often use the byte array type. It stores data in a compact way, with minimal overhead. The syntax must be learned, but it makes sense once it is familiar.