why list.Sort((x ,y) => x - y) has no memory allocation in C#

the C# source code:
text

public void Sort(Comparison<T> comparison) {
    if( comparison == null) {
        ThrowHelper.ThrowArgumentNullException(ExceptionArgument.match);
    }
    Contract.EndContractBlock();

    if( _size > 0) {
        IComparer<T> comparer = new Array.FunctorComparer<T>(comparison);
        Array.Sort(_items, 0, _size, comparer);
    }
}

this line
IComparer<T> comparer = new Array.FunctorComparer<T>(comparison);
shows that every time you sort an array, it will create a new object. But when I ran it many times, I found it has no allocation at all.Why?

Here is my test code.

public static void Main(string[] args)
{
    List<int> list = new List<int>();
    list.Add(1);
    list.Add(2);
    for (int i = 0; i < 10; ++i)
    {
        long cnt = GC.GetTotalMemory(false);
        list.Sort((x ,y) => x - y);
        Console.WriteLine(GC.GetTotalMemory(false) - cnt);
    }
}

It's not clear if you are using .NET 6/7 or .NET Framework 4.x. However, the List<T>.Sort method does allocate memory if you are using .NET Framework 4.x.

Instead of directly using the GC methods, it's far better to use a benchmarking library that is specifically designed to do things like this. I recommend BenchmarkDotNet. For example, a small program like this:

using System.Collections.Generic;
using BenchmarkDotNet.Attributes;
using BenchmarkDotNet.Jobs;
using BenchmarkDotNet.Running;

public static class Program
{
    public static void Main()
    {
        BenchmarkRunner.Run<Benchmarks>();
    }
}

[MemoryDiagnoser] // output memory allocations
[SimpleJob(RuntimeMoniker.Net70)]
[SimpleJob(RuntimeMoniker.Net481)]
public class Benchmarks
{
    private readonly List<int> _list = new List<int>() { 1, 2 };

    [Benchmark]
    public void SortList()
    {
        _list.Sort((x, y) => x - y);
    }
}

Will give you output something like this:

Now you can see that it does indeed allocate either 0 bytes or 24 bytes depending on which framework you are using.