ArrayIterationBenchmarks.cs

using BenchmarkDotNet.Attributes;
using System;
using System.Linq;

namespace ConsoleApp2
{
    [MemoryDiagnoser]
    [DisassemblyDiagnoser(printSource: true)]
    public class ArrayBenchmarks
    {
        int[] array;
        ReadOnlyMemory<int> memory;

        [Params(100)]
        public int Count { get; set; }

        [GlobalSetup]
        public void GlobalSetup()
        {
            array = Enumerable.Range(0, Count).ToArray();
            memory = array.AsMemory();
        }

        [Benchmark(Baseline = true)]
        public int Enumerator()
        {
            var sum = 0;
            foreach (var item in array)
                sum += item;
            return sum;
        }

        [Benchmark]
        public int Indexer()
        {
            var sum = 0;
            for (var index = 0; index < array.Length; index++)
                sum += array[index];
            return sum;
        }

        [Benchmark]
        public int IndexerVar()
        {
            var sum = 0;
            var length = array.Length;
            for (var index = 0; index < length; index++)
                sum += array[index];
            return sum;
        }

        [Benchmark]
        public int Span()
        {
            var span = memory.Span;
            var sum = 0;
            for (var index = 0; index < span.Length; index++)
                sum += span[index];
            return sum;
        }

        [Benchmark]
        public int Memory()
        {
            var sum = 0;
            for (var index = 0; index < memory.Length; index++)
                sum += memory.Span[index];
            return sum;
        }
    }
}