.NET Benchmark and Results for comparing iteration using foreach vs for over ArrayList containing Value Type

ArrayList_for_vs_foreach_Loop_ValueType_Benchmarks.linq

using System;
using System.Collections;
using System.Runtime.CompilerServices;
using BenchmarkDotNet.Attributes;
using BenchmarkDotNet.Columns;
using BenchmarkDotNet.Configs;
using BenchmarkDotNet.Engines;
using BenchmarkDotNet.Running;

[MemoryDiagnoser]
[GroupBenchmarksBy(BenchmarkLogicalGroupRule.ByCategory)]
[CategoriesColumn]
[Config(typeof(IterationBenchmarks.IterationBenchmarksConfig))]
public class IterationBenchmarks
{
	[Params(1_000, 10_000, 50_000)]
	public int Count;

	private ArrayList _arrayList = null;
	private Consumer _consumer = null;

	[GlobalSetup]
	public void GlobalSetup()
	{
		_arrayList = new ArrayList(Count);
		Random random = new Random(42);
		for (int i = 0; i < Count; i++)
		{
			int value = random.Next();
			_arrayList.Add(value);   // boxed
		}

		// Create once and reuse, so you don't benchmark Consumer construction
		_consumer = new Consumer();
	}

	[Benchmark(Baseline = true, Description = "ArrayList<int> foreach")]
	[MethodImpl(MethodImplOptions.NoInlining)]
	public void ArrayList_Foreach()
	{
		foreach (object item in _arrayList)
		{
			int value = (int)item; // unbox
			_consumer.Consume(value);
		}
	}

	[Benchmark(Description = "ArrayList<int> for")]
	[MethodImpl(MethodImplOptions.NoInlining)]
	public void ArrayList_For()
	{
		for (int i = 0; i < _arrayList.Count; i++)
		{
			int value = (int)_arrayList[i]; // indexer returns object -> unbox
			_consumer.Consume(value);
		}
	}

	private class IterationBenchmarksConfig : ManualConfig
	{
		public IterationBenchmarksConfig()
		{
			SummaryStyle = BenchmarkDotNet.Reports.SummaryStyle.Default.WithRatioStyle(RatioStyle.Trend);
		}
	}
}

public static class Program
{
	public static void Main(string[] args)
	{
		BenchmarkRunner.Run<IterationBenchmarks>();
	}
}

Results_NET_10.0.102.txt

// Run time: 00:04:14 (254.71 sec), executed benchmarks: 6
// * Summary *
//
//	BenchmarkDotNet v0.15.8, Windows 11 (10.0.26200.7628/25H2/2025Update/HudsonValley2)
//	AMD Ryzen 9 7945HX with Radeon Graphics 2.50GHz, 1 CPU, 32 logical and 16 physical cores
//
//	.NET SDK 10.0.102
//  [Host] : .NET 10.0.2 (10.0.2, 10.0.225.61305), X86 RyuJIT x86-64-v4
//
//| Method                   | Count | Mean       | Error     | StdDev    | Ratio        | RatioSD | Allocated | Alloc Ratio |
//|------------------------- |------ |-----------:|----------:|----------:|-------------:|--------:|----------:|------------:|
//| 'ArrayList<int> foreach' | 1000  |   4.535 μs | 0.1128 μs | 0.3218 μs |     baseline |         |      28 B |             |
//| 'ArrayList<int> for'     | 1000  |   2.441 μs | 0.0480 μs | 0.0980 μs | 1.86x faster |   0.15x |         - |          NA |
//|                          |       |            |           |           |              |         |           |             |
//| 'ArrayList<int> foreach' | 10000 |  44.173 μs | 0.8891 μs | 2.5652 μs |     baseline |         |      28 B |             |
//| 'ArrayList<int> for'     | 10000 |  23.144 μs | 0.4258 μs | 0.3324 μs | 1.91x faster |   0.11x |         - |          NA |
//|                          |       |            |           |           |              |         |           |             |
//| 'ArrayList<int> foreach' | 50000 | 201.273 μs | 3.6190 μs | 3.2081 μs |     baseline |         |      29 B |             |
//| 'ArrayList<int> for'     | 50000 | 114.972 μs | 2.0725 μs | 1.8372 μs | 1.75x faster |   0.04x |         - |          NA |

Results_NETFramework_4.8.1.txt

// Run time: 00:05:36 (336.18 sec), executed benchmarks: 6
// * Summary *
//
//	BenchmarkDotNet v0.15.8, Windows 11 (10.0.26200.7628/25H2/2025Update/HudsonValley2)
//
//	AMD Ryzen 9 7945HX with Radeon Graphics 2.50GHz, 1 CPU, 32 logical and 16 physical cores
//
//  [Host]     : .NET Framework 4.8.1 (4.8.9221.0), X86 LegacyJIT
//  DefaultJob : .NET Framework 4.8.1 (4.8.9221.0), X86 LegacyJIT
//
//| Method                   | Count | Mean       | Error     | StdDev     | Ratio        | RatioSD | Gen0   | Allocated | Alloc Ratio |
//|------------------------- |------ |-----------:|----------:|-----------:|-------------:|--------:|-------:|----------:|------------:|
//| 'ArrayList<int> foreach' | 1000  |   5.447 μs | 0.0838 μs |  0.0743 μs |     baseline |         | 0.0153 |      28 B |             |
//| 'ArrayList<int> for'     | 1000  |   2.670 μs | 0.1083 μs |  0.3036 μs | 2.06x faster |   0.22x |      - |         - |          NA |
//|                          |       |            |           |            |              |         |        |           |             |
//| 'ArrayList<int> foreach' | 10000 |  58.263 μs | 1.2330 μs |  3.4574 μs |     baseline |         |      - |      28 B |             |
//| 'ArrayList<int> for'     | 10000 |  26.278 μs | 0.5566 μs |  1.6323 μs | 2.23x faster |   0.19x |      - |         - |          NA |
//|                          |       |            |           |            |              |         |        |           |             |
//| 'ArrayList<int> foreach' | 50000 | 283.246 μs | 6.2218 μs | 18.3451 μs |     baseline |         |      - |      28 B |             |
//| 'ArrayList<int> for'     | 50000 | 129.694 μs | 2.5740 μs |  4.9591 μs | 2.19x faster |   0.16x |      - |         - |          NA |