DotnetStringConcatBenchmark/Program.cs

/// dotnet new console
/// dotnet add package BenchmarkDotNet 
/// paste this code in Program.cs
/// dotnet publish -r win10-x64 -c Release
/// run an .exe file

using System;
using System.Collections.Generic;
using System.Text;
using BenchmarkDotNet;
using BenchmarkDotNet.Attributes;
using BenchmarkDotNet.Running;

[MemoryDiagnoser]
public class Program
{
    const int Count = 10000; 

    static void Main(string[] args)
    {
        var summary = BenchmarkRunner.Run<Program>();
    }
    
    [Benchmark]
    public void PlusOperatorConcatTest()
    {
        string str = ""; 
        for (int i = 0; i < Count; i++)
        {
            str += "A"; 
        }
    }

    [Benchmark]
    public void FixedListConcatTest()
    {
        var parts = new List<string>(Count); 
        for (int i = 0; i < Count; i++)
        {
            parts.Add("A"); 
        }

        var str = String.Join(String.Empty, parts); 
    }

    [Benchmark]
    public void UnfixedListConcatTest()
    {
        var parts = new List<string>(); 
        for (int i = 0; i < Count; i++)
        {
            parts.Add("A"); 
        }

        var str = String.Join(String.Empty, parts); 
    }

    [Benchmark]
    public void FixedStringBuilderTest()
    {
        var sb = new StringBuilder(Count);
        for (int i = 0; i < Count; i++)
        {
            sb.Append("A"); 
        }

        var str = sb.ToString(); 
    }

    [Benchmark]
    public void UnfixedStringBuilderTest()
    {
        var sb = new StringBuilder();
        for (int i = 0; i < Count; i++)
        {
            sb.Append("A"); 
        }

        var str = sb.ToString(); 
    }
}