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Sandra Emily
Sandra Emily

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1 Answers

Ashutosh Patel
Ashutosh Patel 13 Jun 2024
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C# Array vs ArrayList

Arrays and ArrayLists are used to store aggregated data but have many differences in features and functionality

Syntax-

Array

int[] arrayName = new int[size];

ArrayList 

ArrayList arrayListName = new ArrayList();

There are several differences between Array and ArrayList as follows,

Type Safety

  • Arrays are type-safe, meaning you specify the type of elements the array can contain when you declare them. Once declared, an array can only contain elements of its specified type.
  •  ArrayLists are not type-safe; You can contain elements of any data type. These variables can cause runtime errors if you try to store incompatible types in an ArrayList.

Resizing

  • Arrays have a fixed size when created. If you need to change the size of an array, you must create a new array of the desired size and copy the elements from the old array to the new array.
  • ArrayLists dynamically resize themselves as needed. They automatically grow or shrink in proportion to the amount of material added or subtracted.

Performance

  • Arrays typically offer better performance than ArrayLists because they have a fixed size and direct access to elements via indexes.
  • ArrayList- If capacity needs to change, there may be some performance overhead due to resizing the ArrayLists process.

Usage

  • Array- If the size of the collection is already known, the arrays are likely to be used extensively and not modified.
  • ArrayLists are used when column size can change or when element type flexibility is needed.

Length Property vs. Count Property

  • Arrays use the Length property to get the number of elements in an Array.
int length = arrayName.Length;
  • ArrayLists use the Count property to get the number of elements in an ArrayList.
int count = arrayListName.Count;

Element Access

  • Arrays provide direct access to elements through indexing.
elementType element = arrayName[index];
  • ArrayLists Provides access to objects using the ArrayList[index] syntax or through methods such as Add, Insert, and Remove.
object element = arrayListName[index];

Example- 

Array 

using System;

class Program
{
    static void Main()
    {
        // Declaring and initializing an array
        int[] numbers = { 1, 2, 3, 4, 5 };

        // Accessing elements from array
        Console.WriteLine("First element: " + numbers[0]);
        Console.WriteLine("Second element: " + numbers[1]);

        // Iterating through loop from array
        Console.WriteLine("\nArray elements are:");
        foreach (int number in numbers)
        {
            Console.WriteLine(number);
        }
        Console.ReadLine();
    }
}

Output-

First element: 1
Second element: 2
Array elements are:
1
2
3
4
5

ArrayList

using System;
using System.Collections;
class Program
{
   static void Main()
   {
       // Creating an ArrayList
       ArrayList arrayList = new ArrayList();
       // Adding elements in the ArrayList
       arrayList.Add("Apple");
       arrayList.Add("Banana");
       arrayList.Add("Orange");
       // Accessing elements from the ArrayList
       Console.WriteLine("First element: " + arrayList[0]);
       Console.WriteLine("Second element: " + arrayList[1]);
       // Iterating through the loop from ArrayList
       Console.WriteLine("\nArrayList elements:");
       foreach (object item in arrayList)
       {
           Console.WriteLine(item);
       }
       Console.ReadLine();
   }
}

Output- 

First element: Apple
Second element: Banana
ArrayList elements:
Apple
Banana
Orange

In summary, Arrays work well and are suitable for fixed-size collections of known types, while ArrayLists offer flexibility and dynamic resizability, making them suitable for situations where collection size may change or where type flexibility is important However, with the introduction of generics in C# (e.g., List<T>), ArrayLists are rare in modern codebases.

Also, Read: Dictionary vs Hashtable in C#

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