Dictionary Comparison for InFlightOperationSet assuming no lock contention

Benchmark.cs

using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using BenchmarkDotNet.Attributes;

namespace Couchbase.LoadTests
{
    public class StatesInFlight
    {
        private readonly Dictionary<uint, object> _dictionary = new Dictionary<uint, object>();

        private readonly ConcurrentDictionary<uint, object> _concurrentDictionary =
            new ConcurrentDictionary<uint, object>();

        private readonly ConcurrentDictionary<uint, object> _concurrentDictionaryLimited =
            new ConcurrentDictionary<uint, object>(2, 16);

        private readonly object _obj = new object();

        private uint _i = 0;

        [Benchmark(Baseline = true)]
        public object ConcurrentDict()
        {
            var i = _i++;
            _concurrentDictionary.TryAdd(i, _obj);
            _concurrentDictionary.TryRemove(i, out var obj);
            return obj;
        }

        /[Benchmark]
        public object Dictionary()
        {
            var i = _i++;

            lock (_obj)
            {
                _dictionary[i] =_obj;
            }

            lock (_obj)
            {
#if NETCOREAPP
                _dictionary.Remove(i, out var obj);
                return obj;
#else
                if (_dictionary.TryGetValue(i, out var obj))
                {
                    _dictionary.Remove(i);
                    return obj;
                }
                else
                {
                    return null;
                }
#endif
            }
        }
    }
}

Benchmark.md

Method	Job	Runtime	Toolchain	Mean	Error	StdDev	Ratio	RatioSD	Rank
ConcurrentDict	Job-NUSUKQ	.NET 4.6.1	net461	96.05 ns	71.593 ns	3.924 ns	1.15	0.03	5
Dictionary	Job-NUSUKQ	.NET 4.6.1	net461	63.69 ns	97.467 ns	5.343 ns	0.76	0.05	3
ConcurrentDict	Job-FGGJBC	.NET Core 2.1	netcoreapp21	82.43 ns	7.113 ns	0.390 ns	0.99	0.01	4
Dictionary	Job-FGGJBC	.NET Core 2.1	netcoreapp21	58.66 ns	95.663 ns	5.244 ns	0.70	0.05	2
ConcurrentDict	Job-GFJGKJ	.NET Core 3.1	netcoreapp31	83.26 ns	27.953 ns	1.532 ns	1.00	0.00	4
Dictionary	Job-GFJGKJ	.NET Core 3.1	netcoreapp31	44.87 ns	10.588 ns	0.580 ns	0.54	0.01	1