PerfTest.cs

using BenchmarkDotNet.Attributes;
using Microsoft.Diagnostics.Tracing.Parsers.Clr;
using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace BenchmarkDotNet.Samples.Forms
{
	[MemoryDiagnoser]
	public class PerfTest
	{
		public List<int> numbers = new List<int>(10) { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 };

		public Func<int, bool> func = x => x % 2 == 0;

		[Benchmark]
		public void LinqWhere()
		{
			numbers.Where(func);
		}

		[Benchmark]
		public void ForEachWhere()
		{
			numbers.Where(func);
		}

		[Benchmark]
		public void WhileWhere()
		{
			numbers.Where(func);
		}
	}


	public static class Other
	{
		public static IEnumerable<T> ForEachWhere<T>(this IEnumerable<T> collection, Func<T, bool> func)
		{
			foreach (var item in collection)
			{
				if (func(item))
					yield return item;
			}
		}

		public static IEnumerable<T> WhileWhere<T>(this IEnumerable<T> collection, Func<T, bool> func)
		{
			var enumerator = ((IEnumerable)collection).GetEnumerator();

			while (enumerator.MoveNext())
			{
				var current = (T)enumerator.Current;

				if (func(current))
					yield return current;
			}
		}

	}
}