C# How to Convert Array to List Easily

In C#, you can convert an array to a list by using List<T> myList = new List<T>(myArray); or var myList = myArray.ToList(); after adding using System.Linq;.

Examples

Input[1, 2, 3]

Output[1, 2, 3]

Input["apple", "banana"]

Output["apple", "banana"]

Input[]

Output[]

How to Think About It

To convert an array to a list, think of the array as a fixed-size collection and the list as a flexible collection. You create a new list and fill it with the elements from the array. This can be done by passing the array to the list constructor or by using a helper method that copies elements.

Algorithm

1

Get the input array.

2

Create a new list and pass the array to its constructor or use a method to convert.

3

Return or use the new list which now contains all elements from the array.

Code

csharp

using System;
using System.Collections.Generic;
using System.Linq;

class Program {
    static void Main() {
        int[] myArray = {1, 2, 3};
        List<int> myList = new List<int>(myArray);
        Console.WriteLine(string.Join(", ", myList));
    }
}

Output

1, 2, 3

Dry Run

Let's trace converting array [1, 2, 3] to a list.

1

Start with array

myArray = [1, 2, 3]

2

Create list from array

myList = new List(myArray) => [1, 2, 3]

3

Print list elements

Output: 1, 2, 3

Step	Array	List
1	[1, 2, 3]	null
2	[1, 2, 3]	[1, 2, 3]
3	[1, 2, 3]	[1, 2, 3]

Why This Works

Step 1: Array to List Constructor

The List<T> constructor accepts an IEnumerable<T>, so passing the array copies all elements into the new list.

Step 2: Using ToList() Method

The ToList() method from System.Linq creates a new list by copying elements from the array.

Step 3: Resulting List

The new list is flexible and can be modified, unlike the fixed-size array.

Alternative Approaches

Using ToList() Extension Method

csharp

using System;
using System.Collections.Generic;
using System.Linq;

class Program {
    static void Main() {
        string[] fruits = {"apple", "banana"};
        List<string> fruitList = fruits.ToList();
        Console.WriteLine(string.Join(", ", fruitList));
    }
}

This method requires <code>using System.Linq;</code> and is concise and readable.

Manual Loop Copy

csharp

using System;
using System.Collections.Generic;

class Program {
    static void Main() {
        int[] numbers = {4, 5, 6};
        List<int> numberList = new List<int>();
        foreach (int num in numbers) {
            numberList.Add(num);
        }
        Console.WriteLine(string.Join(", ", numberList));
    }
}

This approach works without LINQ but is longer and less efficient.

Complexity: O(n) time, O(n) space

Time Complexity

Converting an array to a list requires copying each element once, so it takes linear time proportional to the array size.

Space Complexity

A new list is created with the same number of elements, so extra space proportional to the array size is used.

Which Approach is Fastest?

Using the List<T> constructor or ToList() are equally efficient; manual copying is slower and more verbose.

Approach	Time	Space	Best For
List Constructor	O(n)	O(n)	Simple and efficient conversion
ToList() Method	O(n)	O(n)	Concise and readable with LINQ
Manual Loop Copy	O(n)	O(n)	No LINQ, more control but verbose