C# Essentials

Arrays

type [*]+ array-name = new type [ dimension + ][*]*;

Note: [*] is the set: [] [,] [,,] ...

Arrays allow a group of elements of a particular type to be stored in a contiguous block of memory. Array types derive from System.Array and are declared in C# using left and right brackets ([]). For instance:

char[] vowels = new char[] {'a','e','i','o','u'};
Console.WriteLine(vowels [1]); // Prints "e"

The preceding function call prints “e” because array indexes start at 0. To support other languages, .NET can create arrays based on arbitrary start indexes, but the BCL libraries always use zero-based indexing. Once an array has been created, its length can’t be changed. However, the System.Collection classes provide dynamically sized arrays, as well as other data structures, such as associative (key/value) arrays (see Section 3.4 in Chapter 3).

Multidimensional Arrays

Multidimensional arrays come in two varieties, rectangular and jagged. Rectangular arrays represent an n-dimensional block; jagged arrays are arrays of arrays:

// rectangular
int [,,] matrixR = new int [3, 4, 5]; // creates 1 big cube
// jagged
int [][][] matrixJ = new int [3][][];
for (int i = 0; i < 3; i++) {
   matrixJ[i] = new int [4][];
   for (int j = 0; j < 4; j++)
      matrixJ[i][j] = new int [5];
} 
// assign an element
matrixR [1,1,1] = matrixJ [1][1][1] = 7;

Local and Field Array Declarations

For convenience, local and field declarations can omit the array type when assigning a known value, because the type is specified ...