Distinct vs HashSet benchmark

distinct-vs-hashset-benchmark.cs

#LINQPad optimize+
void Main()
{
	var summary = BenchmarkRunner.Run<DuplicatePerformance>();
}

[MemoryDiagnoser]
public class DuplicatePerformance
{
	private List<int> items;

	[Params(2, 100, 1000)]
	public int SetSize;


	[GlobalSetup]
	public void GlobalSetup()
	{
		Random rd = new Random();
		items = Enumerable.Range(0, SetSize)
			.Select(e => rd.Next(0, SetSize))
			.ToList();
	}

	[Benchmark]
	public int DuplicateInFor()
	{

		List<int> noDuplicates = new List<int>();
		for (int i = 0; i < items.Count; i++)
		{
			int element = items[i];

			if (!noDuplicates.Contains(element))
				noDuplicates.Add(element);
		}
		return noDuplicates.Count;
	}


	[Benchmark]
	public int DuplicateInForeach()
	{

		List<int> noDuplicates = new List<int>();
		foreach (var element in items)
		{
			if (!noDuplicates.Contains(element))
				noDuplicates.Add(element);
		}
		return noDuplicates.Count;
	}

	[Benchmark]
	public int DuplicateWithDistinct()
	{
		List<int> noDuplicates = items.Distinct().ToList();
		return noDuplicates.Count;
	}

	[Benchmark]
	public int DuplicateWithHashSet()
	{
		List<int> noDuplicates = items.ToHashSet().ToList();
		return noDuplicates.Count;
	}

}