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

ArrayList_foreach_vs_List(int)_foreach_ValueType_Benchmarks.linq

[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 List<int> _listOfInt = null;
	private Consumer _consumer = null;

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

		// 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 = "List<int> foreach")]
	[MethodImpl(MethodImplOptions.NoInlining)]
	public void List_Foreach()
	{
		foreach (int item in _listOfInt)
		{
			_consumer.Consume(item);
		}
	}

	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: 00:03:07 (187.09 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  |   4,143.4 ns |    88.30 ns |   257.58 ns |     baseline |         |      28 B |             |
//| 'List<int> foreach'      | 1000  |     569.3 ns |     9.91 ns |    16.01 ns | 7.28x faster |   0.49x |         - |          NA |
//|                          |       |              |             |             |              |         |           |             |
//| 'ArrayList<int> foreach' | 10000 |  39,048.2 ns |   763.83 ns |   938.05 ns |     baseline |         |      28 B |             |
//| 'List<int> foreach'      | 10000 |   5,656.2 ns |   107.70 ns |   105.77 ns | 6.91x faster |   0.21x |         - |          NA |
//|                          |       |              |             |             |              |         |           |             |
//| 'ArrayList<int> foreach' | 50000 | 198,148.2 ns | 3,780.95 ns | 4,354.15 ns |     baseline |         |      29 B |             |
//| 'List<int> foreach'      | 50000 |  27,824.2 ns |   278.48 ns |   217.42 ns | 7.12x faster |   0.16x |         - |          NA |

Results_NETFramework_4.8.1.txt

//	Run time: 00:06:45 (405.59 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  |   5.684 μs | 0.1128 μs |  0.2429 μs |     baseline |         | 0.0153 |      28 B |             |
//| 'List<int> foreach'      | 1000  |   1.694 μs | 0.0321 μs |  0.0812 μs | 3.36x faster |   0.21x |      - |         - |          NA |
//|                          |       |            |           |            |              |         |        |           |             |
//| 'ArrayList<int> foreach' | 10000 |  58.354 μs | 1.1588 μs |  2.5919 μs |     baseline |         |      - |      28 B |             |
//| 'List<int> foreach'      | 10000 |  16.478 μs | 0.3501 μs |  1.0100 μs | 3.55x faster |   0.27x |      - |         - |          NA |
//|                          |       |            |           |            |              |         |        |           |             |
//| 'ArrayList<int> foreach' | 50000 | 276.818 μs | 5.4755 μs | 14.5203 μs |     baseline |         |      - |      28 B |             |
//| 'List<int> foreach'      | 50000 |  80.084 μs | 1.5888 μs |  4.4553 μs | 3.47x faster |   0.26x |      - |         - |          NA |