Arrays (1D, 2D Multidimensional & Jagged) Masterclass

⚡ C# 12 & .NET 8 🟢 Chapter 12 of 35 📂 Phase 5: Strings, Arrays & Collections 📅 2026 Edition

📌 Covered in this chapter: 1D Arrays · Array Indexing & Length · Array.Sort & BinarySearch · Multidimensional [,] Arrays · Jagged Array [][] · Memory Differences

Welcome to Phase 5 (Chapter 12): C# Arrays (1D, 2D Multidimensional & Jagged) Masterclass! An array is a fixed-size collection of elements of the same data type stored in contiguous memory locations. In this chapter, we explore 1D single-dimensional arrays, 2D rectangular multidimensional arrays ([,]), arrays of arrays (jagged arrays [][]), array traversal, sorting, searching, copying, passing arrays to methods, and understanding array limitations.

1Single-Dimensional (1D) Arrays & Array Methods

Array elements are zero-indexed, starting from index 0 up to Length - 1. In C# 8+, you can also use the index-from-end operator ^1 to access the last element directly.

C# — 1D Array Operations ▶ Run in Compiler

// Array declaration and initialization
int[] marks = { 85, 90, 78, 92, 65 };

Console.WriteLine($"Array Length: {marks.Length}");

// Traversing using foreach
foreach (int mark in marks)
{
    Console.WriteLine($"Mark: {mark}");
}

// Array Static Methods: Sort, Reverse, BinarySearch
Array.Sort(marks); // Sorts array in ascending order
Console.WriteLine($"Sorted Min: {marks[0]}, Max: {marks[^1]}"); // ^1 is index from end in C# 8+

int index = Array.BinarySearch(marks, 90);
Console.WriteLine($"Index of 90: {index}");

22D Multidimensional [,] vs Jagged [][] Arrays

C# provides two distinct types of multi-dimensional arrays:

Multidimensional vs Jagged Array Memory Layout: Multidimensional Matrix [2, 3]: Jagged Array [][] (Array of Arrays): ┌────┬────┬────┐ ┌───┐ ┌────┬────┬────┐ │ 10 │ 20 │ 30 │ │ 0 │───►│ 10 │ 20 │ 30 │ (Row 0: len 3) ├────┼────┼────┤ ├───┤ ├────┼────┤ │ 40 │ 50 │ 60 │ │ 1 │───►│ 40 │ 50 │ (Row 1: len 2) └────┴────┴────┘ └───┘ └────┴────┘

C# — 2D Multidimensional & Jagged Arrays ▶ Run in Compiler

// 1. Multidimensional 2D Rectangular Array [rows, cols]
int[,] matrix = {
    { 10, 20, 30 },
    { 40, 50, 60 }
};

Console.WriteLine($"Matrix element [1, 2]: {matrix[1, 2]}"); // 60

// 2. Jagged Array (Array of arrays with variable row lengths)
int[][] jagged = new int[2][];
jagged[0] = new int[] { 1, 2, 3 };
jagged[1] = new int[] { 4, 5 };

Console.WriteLine($"Jagged element [1][0]: {jagged[1][0]}"); // 4

3Passing Arrays to Methods

Arrays are reference types. When you pass an array to a method, the method receives a pointer reference to the original heap array, allowing changes to elements to persist:

C# — Passing Array to Method ▶ Run in Compiler

static void DoubleElements(int[] arr)
{
    for (int i = 0; i < arr.Length; i++)
        arr[i] *= 2;
}

int[] nums = { 1, 2, 3 };
DoubleElements(nums);
Console.WriteLine($"Doubled elements: {string.Join(", ", nums)}"); // 2, 4, 6

4Technical FAQs

Q1: What is the main difference between int[,] and int[][]?

int[,] is a single rectangular block of contiguous memory where every row has the same number of columns. int[][] is an array of separate array references, allowing rows of varying lengths.

Q2: Can arrays be resized in C#?

No. Arrays are fixed in size once instantiated. Array.Resize() actually allocates a brand new array under the hood and copies elements over.