Arrays, memory. Arrays are memory-efficient. Lists are built on top of arrays. Because of this, Lists use more memory to store the same data.

We provide a detailed comparison of array and List memory usage. A simple benchmark can be used to measure the memory of lists and arrays.

We focus on how the 2 data structures perform. The 2 code examples contrast how you can use an array with more complex logic, and a List with simpler logic.

List Add

int Array

using System.Collections.Generic;

class Program
{
    static void Main()
    {
        // Compare time to build up a List.
        List<int> list = new List<int>();
        for (int i = 0; i < 60000; i++)
        {
            list.Add(i);
        }
    }
}
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        // Compare time to allocate an array and assign to it.
        int[] array = new int[60000];
        for (int i = 0; i < 60000; i++)
        {
            array[i] = i;
        }
    }
}
List generic:  6.172 MB
Integer array: 5.554 MB
List generic:  1043.4 ms
Integer array:  980.2 ms

Discussion. Arrays and Lists can change performance and memory usage. The benchmarks were taken from a more complex program, but they show the pattern of arrays being more efficient.

Notes, generics. You might be able to convert from generics to arrays. You could store the size of the array and use it when initializing later. That way you don't have to resize anything.

Generic

Summary. We saw a comparison of List and array memory usage in the C# language. For speed it is sometimes worthwhile to prefer regular arrays. The performance benefit is significant.