6.1 Arrays

Let’s go through arrays in C# — a fundamental way to store multiple values of the same type.

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📌 1. What is an Array?

• An array is a collection of elements of the same type stored in contiguous memory locations.

• Each element is accessed by an index, starting at 0.

• Fixed size (cannot grow/shrink dynamically).

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📌 2. Declaring and Initializing Arrays

Syntax

type[] arrayName;        // Declaration
arrayName = new type[size]; // Initialization

Example 1: Declare and Initialize Separately

int[] numbers;          // Declaration
numbers = new int[5];   // Array of 5 integers
numbers[0] = 10;
numbers[1] = 20;

Example 2: Declare and Initialize Together

int[] numbers = new int[5] { 1, 2, 3, 4, 5 };
string[] names = { "Alice", "Bob", "Charlie" }; // Implicit size

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📌 3. Accessing Array Elements

int[] numbers = { 10, 20, 30, 40, 50 };
Console.WriteLine(numbers[0]); // 10
numbers[2] = 35;               // Update element at index 2
Console.WriteLine(numbers[2]); // 35

• Index starts at 0

• Last element = length - 1

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📌 4. Array Properties & Methods

Property / Method	Description	Example
Length	Number of elements in the array	numbers.Length
Rank	Number of dimensions	numbers.Rank
Clone()	Creates a copy of the array	int[] copy = (int[])numbers.Clone();
Array.Sort()	Sorts the array	Array.Sort(numbers);
Array.Reverse()	Reverses the array	Array.Reverse(numbers);

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📌 5. Multidimensional Arrays

2D Array (Matrix)

int[,] matrix = new int[2,3] { {1,2,3}, {4,5,6} };
Console.WriteLine(matrix[1,2]); // 6

Jagged Array (Array of Arrays)

int[][] jagged = new int[2][];
jagged[0] = new int[] {1, 2};
jagged[1] = new int[] {3, 4, 5};
 
Console.WriteLine(jagged[1][2]); // 5

• Multidimensional array → rectangular

• Jagged array → each “row” can have different lengths

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📌 6. Iterating Through Arrays

int[] numbers = { 1, 2, 3, 4, 5 };
 
// Using for loop
for (int i = 0; i < numbers.Length; i++)
{
    Console.WriteLine(numbers[i]);
}
 
// Using foreach loop
foreach (int num in numbers)
{
    Console.WriteLine(num);
}

• for → use index

• foreach → simpler, read-only access

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📌 7. Summary Table

Feature	Description
Declaration	int[] arr;
Initialization	arr = new int[5]; or int[] arr = {1,2,3};
Access	arr[index]
Length	arr.Length
Multidimensional	int[,] matrix
Jagged Arrays	int[][] jagged
Iteration	for or foreach

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✅ Tip:

• Use arrays when size is fixed and elements are of the same type

• For dynamic collections, consider List instead of arrays