Simple LinqPad sample of how to execute a performance test in C#

PerfTest.cs

void Main()
{
	var messageCount = 10000;
	var sum =0L;
	var result = ThroughputTestResult.Capture(messageCount, () => sum = SumOfSquares(messageCount));
	Console.WriteLine($"Result: SumOfSquares({messageCount}) = {sum}");
	
	Console.WriteLine(result.ToString());
}

// Define other methods and classes here
public static long SumOfSquares(int max)
{
	var sum = 0L;
	for (long i = 0; i < max; i++)
		sum += i * i;
	return sum;
}

public sealed class GcInfo
{
	public static GcInfo Current()
	{
		return new GcInfo(GC.CollectionCount(0), GC.CollectionCount(1), GC.CollectionCount(2), GC.GetTotalMemory(forceFullCollection: false));
	}

	public int Gen0 { get; }
	public int Gen1 { get; }
	public int Gen2 { get; }
	public long TotalBytesAllocated { get; }

	public GcInfo(int gen0, int gen1, int gen2, long totalBytesAllocated)
	{
		Gen0 = gen0;
		Gen1 = gen1;
		Gen2 = gen2;
		TotalBytesAllocated = totalBytesAllocated;
	}

	public GcInfo Delta(GcInfo previous)
	{
		return new GcInfo(Gen0 - previous.Gen0, Gen1 - previous.Gen1, Gen2 - previous.Gen2, TotalBytesAllocated - previous.TotalBytesAllocated);
	}
}
public sealed class ThroughputTestResult
{
	public long Messages { get; private set; }
	public TimeSpan Elapsed { get; private set; }
	public GcInfo GarbageCollections { get; private set; }

	public static ThroughputTestResult Capture(long messages, Action action)
	{
		GC.Collect();
		GC.WaitForPendingFinalizers();
		GC.Collect();

		var initial = GcInfo.Current();
		var start = Stopwatch.GetTimestamp();
		action();
		var elapsedTicks = Stopwatch.GetTimestamp() - start;
		var gcDelta = GcInfo.Current().Delta(initial);

		return new ThroughputTestResult
		{
			Messages = messages,
			Elapsed = TimeSpan.FromTicks(elapsedTicks),
			GarbageCollections = gcDelta
		};
	}

	public override string ToString()
	{
		return $"Messages='{Messages:N0}', Elapsed='{Elapsed}', msg/sec={(Messages / Elapsed.TotalSeconds):N}, GC[0]={GarbageCollections.Gen0},[1]={GarbageCollections.Gen1},[2]={GarbageCollections.Gen2},[BytesAllocated]={GarbageCollections.TotalBytesAllocated:N0}";
	}
}