C# 4.0 Pocket Reference, 3rd Edition

Arrays

An array represents a fixed number of elements of a particular type. The elements in an array are always stored in a contiguous block of memory, providing highly efficient access.

An array is denoted with square brackets after the element type. The following declares an array of 5 characters:

char[] vowels = new char[5];

Square brackets also index the array, accessing a particular element by position:

vowels[0] = 'a'; vowels[1] = 'e'; vowels[2] = 'i';
vowels[3] = 'o'; vowels[4] = 'u';

Console.WriteLine (vowels [1]);      // e

This prints “e” because array indexes start at 0. We can use a for loop statement to iterate through each element in the array. The for loop in this example cycles the integer i from 0 to 4:

for (int i = 0; i < vowels.Length; i++)
  Console.Write (vowels [i]);            // aeiou

Arrays also implement IEnumerable<T> (see Enumeration and Iterators), so you can also enumerate members with the foreach statement:

foreach (char c in vowels) Console.Write (c);  // aeiou

All array indexing is bounds-checked by the runtime. An IndexOutOfRangeException is thrown if you use an invalid index:

vowels[5] = 'y';   // Runtime error

The Length property of an array returns the number of elements in the array. Once an array has been created, its length cannot be changed. The System.Collection namespace and subnamespaces provide higher-level data structures, such as dynamically sized arrays and dictionaries.

An array initialization expression lets you declare and populate an array in a single step:

char[] ...