NWoodsman

const int SIZE = 1_000_000;
const int HALF_SIZE = 500_000;

[Benchmark]
public void ms_mutable_list()
{
    var ms_list = new List<int>();
    for (int i = 0; i < SIZE; i++) ms_list.Add(i);
}

NWoodsman

<Window
    x:Class="WpfApp1.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:local="clr-namespace:WpfApp1"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    Title="MainWindow"
    Width="800"
    Height="450"