Array traversal: for vs. LINQ

ArrayTraverse.cs

using System;
using System.Diagnostics;

int[,] a = {
    {1,2,3,4,5,6,7,8},
    {4,5,6,7,8,9,10,1},
    {7,8,9,10,11,12,13,14},
    {10,1,2,3,4,5,6,7},
    {1,2,3,4,5,6,7,8},
    {4,5,6,7,8,9,10,1},
    {7,8,9,10,11,12,13,14},
    {10,1,2,3,4,5,6,7},
    {1,2,3,4,5,6,7,8},
    {4,5,6,7,8,9,10,1},
    {7,8,9,10,11,12,13,14},
    {10,1,2,3,4,5,6,7},
    {1,2,3,4,5,6,7,8},
    {4,5,6,7,8,9,10,1},
    {7,8,9,10,11,12,13,14},
    {10,1,2,3,4,5,6,7}
};

var sw = new Stopwatch();
sw.Start();
var count = 0;
for (int i = 0; i < a.GetLength(0); i++)
{
    for (int j = 0; j < a.GetLength(1); j++)
        if (a[i,j] == 1)
            count++;
}
Console.WriteLine(count);
sw.Stop();
Console.WriteLine($"for loops: {sw.ElapsedMilliseconds}ms");


sw = new Stopwatch();
sw.Start();
var xRange = Enumerable.Range(0, a.GetLength(0));
var yRange = Enumerable.Range(0, a.GetLength(1));
var result = xRange.SelectMany(x => yRange.Select(y => a[x, y]));
var count2 = result.Count(x => x == 1);
Console.WriteLine(count2);
sw.Stop();
Console.WriteLine($"LINQ: {sw.ElapsedMilliseconds}ms");



var list = new List<List<int>> {
    new() {1,2,3,4,5,6,7,8},
    new() {4,5,6,7,8,9,10,1},
    new() {7,8,9,10,11,12,13,14},
    new() {10,1,2,3,4,5,6,7},
    new() {1,2,3,4,5,6,7,8},
    new() {4,5,6,7,8,9,10,1},
    new() {7,8,9,10,11,12,13,14},
    new() {10,1,2,3,4,5,6,7},
    new() {1,2,3,4,5,6,7,8},
    new() {4,5,6,7,8,9,10,1},
    new() {7,8,9,10,11,12,13,14},
    new() {10,1,2,3,4,5,6,7},
    new() {1,2,3,4,5,6,7,8},
    new() {4,5,6,7,8,9,10,1},
    new() {7,8,9,10,11,12,13,14},
    new() {10,1,2,3,4,5,6,7}
};
sw = new Stopwatch();
sw.Start();
var count3 = list.Select(x => x.Count(y => y == 1)).Sum();
Console.WriteLine(count3);
sw.Stop();
Console.WriteLine($"List<List<int>> LINQ: {sw.ElapsedMilliseconds}ms");