benchmark.txt

BenchmarkDotNet=v0.12.0, OS=Windows 10.0.17763.805 (1809/October2018Update/Redstone5), VM=VMware
Intel Core i7-7700K CPU 4.20GHz (Kaby Lake), 1 CPU, 4 logical and 4 physical cores
  [Host]     : .NET Framework 4.8 (4.8.4018.0), X86 LegacyJIT
  DefaultJob : .NET Framework 4.8 (4.8.4018.0), X86 LegacyJIT


|         Method | Count |        Mean |     Error |    StdDev | Rank |
|--------------- |------ |------------:|----------:|----------:|-----:|
|       IntArray |  1000 |    260.9 ns |   3.25 ns |   3.04 ns |    1 |
|    StringArray |  1000 |  3,372.6 ns |  25.71 ns |  22.79 ns |    4 |
| StringBoxArray |  1000 |  1,504.0 ns |  18.43 ns |  17.24 ns |    2 |
|       IntArray | 10000 |  2,985.6 ns |  27.66 ns |  25.87 ns |    3 |
|    StringArray | 10000 | 33,456.6 ns | 315.20 ns | 294.84 ns |    6 |
| StringBoxArray | 10000 | 14,966.4 ns | 127.60 ns | 119.36 ns |    5 |


BenchmarkDotNet=v0.12.0, OS=Windows 10.0.17763.805 (1809/October2018Update/Redstone5), VM=VMware
Intel Core i7-7700K CPU 4.20GHz (Kaby Lake), 1 CPU, 4 logical and 4 physical cores
  [Host]     : .NET Framework 4.8 (4.8.4018.0), X64 RyuJIT
  DefaultJob : .NET Framework 4.8 (4.8.4018.0), X64 RyuJIT


|         Method | Count |        Mean |     Error |    StdDev | Rank |
|--------------- |------ |------------:|----------:|----------:|-----:|
|       IntArray |  1000 |    422.6 ns |   8.46 ns |  11.29 ns |    1 |
|    StringArray |  1000 |  1,987.8 ns |  17.91 ns |  15.87 ns |    3 |
| StringBoxArray |  1000 |  1,721.7 ns |  22.09 ns |  19.59 ns |    2 |
|       IntArray | 10000 |  4,146.9 ns |  34.87 ns |  32.61 ns |    4 |
|    StringArray | 10000 | 19,900.7 ns | 181.12 ns | 169.42 ns |    6 |
| StringBoxArray | 10000 | 17,193.7 ns | 108.32 ns | 101.33 ns |    5 |

foo.cs

using BenchmarkDotNet.Attributes;
using BenchmarkDotNet.Running;

public struct StringBox {
  public string Value;
}

[RankColumn]
public class ArraysBenchmark {
  private int[] intArray;
  private string[] stringArray;
  private StringBox[] stringBoxArray;

  [Params(1000, 10000)]
  public int Count;

  [GlobalSetup]
  public void Setup() {
    intArray = new int[Count];
    stringArray = new string[Count];
    stringBoxArray = new StringBox[Count];
  }

  [Benchmark]
  public void IntArray() {
    var array = intArray;
    for (var index = 0; index < array.Length; index++) {
      array[index] = 42;
    }
  }

  [Benchmark]
  public void StringArray() {
    var array = stringArray;
    for (var index = 0; index < array.Length; index++) {
      array[index] = "42";
    }
  }

  [Benchmark]
  public void StringBoxArray() {
    var array = stringBoxArray;
    for (var index = 0; index < array.Length; index++) {
      array[index].Value = "42";
    }
  }
}

public class Program {
  public static void Main(string[] args) {
    BenchmarkRunner.Run<ArraysBenchmark>();
  }
}