C# Array vs List: When should you use an array or a List?

C# Array vs List: A List<T> is a generic collection that can resize automatically as elements are added and removed, whereas an array is a fixed-size sequential collection of the same type of elements.

Table of Contents

Array

C# Array : Arrays are strongly typed collections of the same data type with a fixed length that cannot be modified during execution. Array elements are accessed using numeric indexes and start at zero. The default value for numeric array items is zero, while the default value for reference array elements is null.

The array is in the System.Array namespace. It must be specified in brackets[], with the type of variables it will carry ( integer, string etc. ) and the name of the array.
The following is the example of how to define an array of integers with the name intArray:

Create an Array

int[] intArray = new int[5]; // Array having a length of 5

int[] intArray = new int[] {10, 20, 30, 40, 50 };

Access the elements of an Array

You can create a string array with the following syntax:

using System;
namespace CSharpArrayExample
{
    public class CSharpArrayExample
    {   
        static void Main(string[] args)
        {
            // Declare an array
            string[] fruitsName = { "Apple", "Orange", "Banana", "Grapes"};

            // Access the elements of an Array using index
            Console.WriteLine(fruitsName[0]); // Output: Apple

            // Access the elements using for loop
            for(int index = 0; index < fruitsName.Length; index ++)
            {
                Console.WriteLine(fruitsName[index]);
            }

            Console.ReadKey();
        }
        //Output:
        // Apple
        // Orange
        // Banana
        // Grapes
    }
}

C# List

List<T>: In C#, the List is a generic type used to represent the collection of strongly typed objects that can be accessed via index or loops. The List class is available in the System.Collection.Generic namespace.
It allows you to search, sort, manipulate, add, and remove elements from the collection of strongly typed objects.
C# List has so many additional characteristics, such as the ability to resize dynamically when an element is added or removed.

Please check my previous blog for more information about the list: C# List Class

Syntax

The following is the syntax for declaring a generic List< T >. The parameter T in the List represents the type of item in the list, which can be int, long, string, or any user-defined object.

List<T> myList = new List<T>();

C# List<T> example

The following is an example of List in C#

using System;
using System.Collections.Generic;
namespace CSharpListExample
{
    public class CSharpArrayExample
    {   
        static void Main(string[] args)
        {
            // Declare a generic List of string type
            List<string> fruitsName = new List<string>();
           // Add items in the List

            fruitsName.Add("Apple");
            fruitsName.Add("Orange");
            fruitsName.Add("Banana");
            fruitsName.Add("Grapes");
            
            // Access the elements of a List using index
            Console.WriteLine(fruitsName[0]); // Output: Apple

            // Access the list elements using for loop
            for(int index = 0; index < fruitsName.Count; index ++)
            {
                Console.WriteLine(fruitsName[index]);
            }

            Console.ReadKey();
        }
        //Output:
        // Apple
        // Orange
        // Banana
        // Grapes
    }
}

C# Array vs List Comparison

Parameters	C# List	C# Array
1. Length	A list in C# can be dynamically resized when items are added or removed.	The size of an array is fixed, therefore it can only store a fixed number of elements of the same data type.
2. Namespace	C# List class comes under the System.Collection.Generic namespace	Array belongs to the System.Array namespace
3. Memory	List memory is dynamic and random. List occupies more memory than Array since each node defined the List has its own memory set.	Array memory is static and continuous. Arrays are memory efficient.
4. Usage	A list is useful when elements are frequently added and removed.	Arrays are handy when you have a fixed number of elements that are unlikely to change and want to access them frequently in a non-sequential way.
5. Speed	Slower in Execution.	An array is faster in Execution.
6. Memory management	With C# List, there is no memory wastage .	Memory wastage is a problem with arrays. Many of the memory blocks assigned to an array stay unused until new items are added after fixed-sized memory has been allocated. Furthermore, they can’t be assigned to other processes, which leads to memory waste.
7. Memory Structure	In C# List, Non-Contiguous Memory Allocation is performed. Non-Contiguous Memory Allocation separates the process into various blocks, which are subsequently placed in different address spaces of the memory depending on memory space availability. Non-contiguous memory allocation is demonstrated by paging and segmentation.	In C# Array, Contiguous Memory Allocation is performed. The contiguous Memory Allocation technique allocates a single contiguous block of memory to a process based on its requirements. The *memory space is divided into fixed-sized partitions*, and each partition is assigned to just one process.

C# Array vs List

References: C# Array, C# List

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