0_benchmarks.cs

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

namespace dictionary_vs_array
{
    public class Benchmarks
    {
        [Params(1, 3, 5, 10, 20, 50, 100)]
        public int NumItems { get; set; }

        [Params(1, 1000)]
        public int StringLength { get; set; }

        private string[] arrayData;
        private Dictionary<string, string> dictionaryData;

        [GlobalSetup]
        public void GlobalSetup()
        {
            arrayData = new string[NumItems];
            dictionaryData = new Dictionary<string, string>(NumItems);
            for (int i = 0; i < NumItems; i++)
            {
                var value = new string((char)('a' + i), StringLength);
                arrayData[i] = value;
                dictionaryData[value] = null;
            }
        }

        [Benchmark]
        public bool ArrayLinearSearch()
        {
            var result = true;
            for (int i = 0; i < NumItems; i++)
            {
                result &= Array.IndexOf(arrayData, arrayData[i]) >= 0;
            }
            return result;
        }

        [Benchmark]
        public bool DictionaryLookup()
        {
            var result = true;
            for (int i = 0; i < NumItems; i++)
            {
                result &= dictionaryData.ContainsKey(arrayData[i]);
            }
            return result;
        }
    }
}

1_results.txt

// * Summary *

BenchmarkDotNet=v0.12.0, OS=Windows 10.0.19042
AMD Ryzen 9 3900XT, 1 CPU, 24 logical and 12 physical cores
.NET Core SDK=5.0.102
  [Host]     : .NET Core 3.1.11 (CoreCLR 4.700.20.56602, CoreFX 4.700.20.56604), X64 RyuJIT
  DefaultJob : .NET Core 3.1.11 (CoreCLR 4.700.20.56602, CoreFX 4.700.20.56604), X64 RyuJIT


|            Method | NumItems | StringLength |         Mean |      Error |     StdDev |
|------------------ |--------- |------------- |-------------:|-----------:|-----------:|
| ArrayLinearSearch |        1 |            1 |     12.11 ns |   0.072 ns |   0.060 ns |
|  DictionaryLookup |        1 |            1 |     12.86 ns |   0.245 ns |   0.229 ns |
| ArrayLinearSearch |        1 |         1000 |     11.75 ns |   0.046 ns |   0.043 ns |
|  DictionaryLookup |        1 |         1000 |    209.88 ns |   0.333 ns |   0.278 ns |
| ArrayLinearSearch |        3 |            1 |     47.07 ns |   0.267 ns |   0.249 ns |
|  DictionaryLookup |        3 |            1 |     37.14 ns |   0.245 ns |   0.218 ns |
| ArrayLinearSearch |        3 |         1000 |     45.75 ns |   0.472 ns |   0.442 ns |
|  DictionaryLookup |        3 |         1000 |    655.17 ns |   3.568 ns |   3.337 ns |
| ArrayLinearSearch |        5 |            1 |    107.64 ns |   0.625 ns |   0.585 ns |
|  DictionaryLookup |        5 |            1 |     61.30 ns |   0.406 ns |   0.380 ns |
| ArrayLinearSearch |        5 |         1000 |    105.98 ns |   1.803 ns |   1.687 ns |
|  DictionaryLookup |        5 |         1000 |  1,073.08 ns |   3.237 ns |   2.527 ns |
| ArrayLinearSearch |       10 |            1 |    362.17 ns |   2.359 ns |   1.970 ns |
|  DictionaryLookup |       10 |            1 |    121.88 ns |   1.280 ns |   1.198 ns |
| ArrayLinearSearch |       10 |         1000 |    353.33 ns |   3.352 ns |   3.135 ns |
|  DictionaryLookup |       10 |         1000 |  2,234.56 ns |   8.399 ns |   7.445 ns |
| ArrayLinearSearch |       20 |            1 |  1,269.12 ns |  24.956 ns |  39.583 ns |
|  DictionaryLookup |       20 |            1 |    276.19 ns |   1.474 ns |   1.379 ns |
| ArrayLinearSearch |       20 |         1000 |  1,152.46 ns |   9.778 ns |   8.668 ns |
|  DictionaryLookup |       20 |         1000 |  4,387.22 ns |  31.847 ns |  29.789 ns |
| ArrayLinearSearch |       50 |            1 |  6,599.39 ns | 108.039 ns |  95.774 ns |
|  DictionaryLookup |       50 |            1 |    761.05 ns |   2.331 ns |   2.067 ns |
| ArrayLinearSearch |       50 |         1000 |  6,257.57 ns |  64.792 ns |  60.606 ns |
|  DictionaryLookup |       50 |         1000 | 11,029.63 ns | 108.646 ns | 101.627 ns |
| ArrayLinearSearch |      100 |            1 | 25,399.07 ns | 460.248 ns | 430.516 ns |
|  DictionaryLookup |      100 |            1 |  1,282.42 ns |  16.019 ns |  14.984 ns |
| ArrayLinearSearch |      100 |         1000 | 22,699.34 ns | 142.476 ns | 133.272 ns |
|  DictionaryLookup |      100 |         1000 | 22,072.53 ns | 160.632 ns | 150.255 ns |

// * Hints *
Outliers
  Benchmarks.ArrayLinearSearch: Default -> 2 outliers were removed (13.89 ns, 14.01 ns)
  Benchmarks.DictionaryLookup: Default  -> 2 outliers were removed (212.30 ns, 213.99 ns)
  Benchmarks.ArrayLinearSearch: Default -> 1 outlier  was  detected (48.05 ns)
  Benchmarks.DictionaryLookup: Default  -> 1 outlier  was  removed (57.55 ns)
  Benchmarks.DictionaryLookup: Default  -> 3 outliers were removed (1.08 us..1.09 us)
  Benchmarks.ArrayLinearSearch: Default -> 2 outliers were removed (372.92 ns, 373.19 ns)
  Benchmarks.DictionaryLookup: Default  -> 1 outlier  was  removed (2.27 us)
  Benchmarks.ArrayLinearSearch: Default -> 1 outlier  was  removed (1.43 us)
  Benchmarks.ArrayLinearSearch: Default -> 1 outlier  was  removed (1.19 us)
  Benchmarks.ArrayLinearSearch: Default -> 1 outlier  was  removed (6.84 us)
  Benchmarks.DictionaryLookup: Default  -> 1 outlier  was  removed (770.79 ns)
  Benchmarks.ArrayLinearSearch: Default -> 1 outlier  was  detected (22.40 us)

// * Legends *
  NumItems     : Value of the 'NumItems' parameter
  StringLength : Value of the 'StringLength' parameter
  Mean         : Arithmetic mean of all measurements
  Error        : Half of 99.9% confidence interval
  StdDev       : Standard deviation of all measurements
  1 ns         : 1 Nanosecond (0.000000001 sec)

// ***** BenchmarkRunner: End *****
// ** Remained 0 benchmark(s) to run **
Run time: 00:09:06 (546.59 sec), executed benchmarks: 28

Global total time: 00:09:10 (550.02 sec), executed benchmarks: 28

2_program.cs

using BenchmarkDotNet.Running;

namespace dictionary_vs_array
{
    public class Program
    {
        public static void Main(string[] args)
        {
            var summary = BenchmarkRunner.Run<Benchmarks>();
        }
    }
}

3_dictionary-vs-array.csproj

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <TargetFramework>netcoreapp3.0</TargetFramework>
    <OutputType>Exe</OutputType>
  </PropertyGroup>
  <PropertyGroup>
    <PlatformTarget>AnyCPU</PlatformTarget>
    <DebugType>portable</DebugType>
    <DebugSymbols>true</DebugSymbols>
    <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
    <Optimize>true</Optimize>
    <Configuration>Release</Configuration>
  </PropertyGroup>
  <ItemGroup>
    <PackageReference Include="BenchmarkDotNet" Version="0.12.0" />
    <PackageReference Include="BenchmarkDotNet.Diagnostics.Windows" Version="0.12.0"/>
  </ItemGroup>
</Project>