Arrays And Lists In C# Complete Guide

Arrays in C#

Example 1: Declaring, Initializing, and Accessing an Array

1. Declare an Array: Define the type of elements and the size of the array.
2. Initialize an Array: Assign values to each element.
3. Access Elements: Retrieve values using their index.
4. Modify Elements: Change values at specific indices.

using System;

class Program
{
    static void Main()
    {
        // Step 1: Declare an array of integers with a size of 5
        int[] numbers;
        numbers = new int[5];

        // Step 2: Initialize the array elements
        numbers[0] = 10;
        numbers[1] = 20;
        numbers[2] = 30;
        numbers[3] = 40;
        numbers[4] = 50;

        // You can also initialize an array at the time of declaration as follows:
        // int[] numbers = { 10, 20, 30, 40, 50 };

        // Step 3: Access elements and print them
        Console.WriteLine("Array elements:");
        for (int i = 0; i < numbers.Length; i++)
        {
            Console.WriteLine("Element at index " + i + ": " + numbers[i]);
        }

        // Step 4: Modify elements
        numbers[2] = 100;
        Console.WriteLine("Modified array element at index 2: " + numbers[2]);
    }
}

Explanation:

• Declaration: int[] numbers; declares an uninitialized array of integers named numbers.
• Initialization: numbers = new int[5]; initializes the array with a size of 5.
• Accessing Elements: numbers[i] accesses the element at index i. The Length property returns the number of elements in the array.
• Modifying Elements: numbers[2] = 100; changes the value at index 2 from 30 to 100.

Lists in C#

Example 1: Declaring, Initializing, Adding, and Accessing Elements in a List

1. Include the Namespace: Import System.Collections.Generic to use the List<T> class.
2. Declare and Initialize a List: Define the type of elements in the list.
3. Add Elements: Use methods like Add() to insert items into the list.
4. Insert Elements: Insert an item at a specified index with Insert().
5. Remove Elements: Delete an element by its value with Remove(), or by index with RemoveAt().
6. Access Elements: Use indexing similar to arrays.
7. Iterate through a List: Use loops to access all elements.

using System;
using System.Collections.Generic; // Step 1: Include this namespace

class Program
{
    static void Main()
    {
        // Step 2: Declare and initialize a list of strings
        List<string> fruits = new List<string>();

        // Step 3: Add elements to the list
        fruits.Add("Apple");
        fruits.Add("Banana");
        fruits.Add("Cherry");

        // Step 4: Insert an element at index 1
        fruits.Insert(1, "Blueberry");

        // Print the list
        Console.WriteLine("List elements after insertion:");
        foreach (string fruit in fruits)
        {
            Console.WriteLine(fruit);
        }

        // Step 5: Remove an element by its value
        fruits.Remove("Banana");

        // Print the list
        Console.WriteLine("List elements after removal:");
        foreach (string fruit in fruits)
        {
            Console.WriteLine(fruit);
        }

        // Step 5: Remove an element by its index
        fruits.RemoveAt(0);

        // Print the list
        Console.WriteLine("List elements after removing first element:");
        foreach (string fruit in fruits)
        {
            Console.WriteLine(fruit);
        }

        // Step 6: Access elements
        string secondFruit = fruits[1];
        Console.WriteLine("Second fruit in the list: " + secondFruit);

        // Step 7: Iterate through the list
        Console.WriteLine("All elements in the list:");
        for (int i = 0; i < fruits.Count; i++)
        {
            Console.WriteLine("Element at index " + i + ": " + fruits[i]);
        }
    }
}

Explanation:

• Namespace: We include System.Collections.Generic to use the List<T> class.
• Declaration and Initialization: List<string> fruits = new List<string>(); creates an empty list that will hold strings.
• Add Elements: fruits.Add("Apple"); adds "Apple" to the end of the list.
• Insert Elements: fruits.Insert(1, "Blueberry"); inserts "Blueberry" at index 1.
• Remove Elements: fruits.Remove("Banana"); and fruits.RemoveAt(0); remove elements from the list by value and by index respectively.
• Accessing Elements: fruits[1] accesses the element at index 1.
• Iterating through a List: foreach loop and for loop iterate through all elements in the list.

Additional Features

Example 2: Multi-dimensional Arrays and Jagged Arrays (Advanced)

Multi-dimensional Arrays: Arrays with more than one dimension are known as multi-dimensional arrays.

using System;

class Program
{
    static void Main()
    {
        // Declare and initialize a 2D array
        int[,] matrix = new int[2, 3]
        {
            { 1, 2, 3 },
            { 4, 5, 6 }
        };

        // Print elements of the 2D array
        Console.WriteLine("2D Array elements:");
        for (int i = 0; i < matrix.GetLength(0); i++) 
        {
            for (int j = 0; j < matrix.GetLength(1); j++)
            {
                Console.Write(matrix[i, j] + " ");
            }
            Console.WriteLine();
        }
    }
}

Jagged Arrays: An array of arrays, where each inner array can be of different lengths.

using System;

class Program
{
    static void Main()
    {
        // Declare and initialize a jagged array
        int[][] jaggedArray = new int[3][];
        jaggedArray[0] = new int[] { 1, 2, 3 };
        jaggedArray[1] = new int[] { 4, 5 };
        jaggedArray[2] = new int[] { 6, 7, 8, 9 };

        // Print elements of the jagged array
        Console.WriteLine("Jagged Array elements:");
        for (int i = 0; i < jaggedArray.Length; i++)
        {
            for (int j = 0; j < jaggedArray[i].Length; j++)
            {
                Console.Write(jaggedArray[i][j] + " ");
            }
            Console.WriteLine();
        }
    }
}

Explanation:

• Multi-dimensional Arrays: We use commas to separate dimensions, e.g., int[,] matrix.
• Jagged Arrays: Each element of the outer array is another array, which can have a different length.
• GetLength(): matrix.GetLength(0) returns the number of rows, while matrix.GetLength(1) returns the number of columns.

Conclusion