Performance Benchmarks for String Concatenation

ReadMe.md

Performance Benchmarks for String Concatenation

Reading

• String Interpolation in C# 10 and .NET 6 - .NET Blog
• BenchmarkDotNet

output.log

| Method                           | Lines | Mean     | Ratio | Allocated  | 
|--------------------------------- |------ |---------:|------:|-----------:|
| Option_A_Chained_Appends         | 10000 | 102.0 us |  0.86 |  935.62 KB | 
| Option_B_AppendFormat            | 10000 | 204.9 us |  1.73 | 1169.99 KB | 
| Option_C_Interpolated_AppendLine | 10000 | 118.8 us |  1.00 |  935.62 KB | 

Program.cs

using System.Text;
using BenchmarkDotNet.Attributes;
using BenchmarkDotNet.Columns;
using BenchmarkDotNet.Running;

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

[MemoryDiagnoser] // reports allocations, too
[HideColumns(
    Column.Error,
    Column.StdDev,
    Column.RatioSD,
    Column.AllocRatio,
    Column.Gen0,
    Column.Gen1,
    Column.Gen2)]
public class StringBuilderSuite
{
    // How many lines to build per benchmark. Adjust if you want a longer/shorter run.
    [Params(10_000)]
    public int Lines;

    // Rough preallocation to avoid resize noise; tweak if you change the format a lot.
    private int EstimatedPerLine => 24;

    [Benchmark]
    public string Option_A_Chained_Appends()
    {
        var sb = new StringBuilder(Lines * EstimatedPerLine);
        for (int i = 0; i < Lines; i++)
        {
            sb.Append("remapping ").Append(i).AppendLine(" synonyms");
        }
        return sb.ToString();
    }

    [Benchmark]
    public string Option_B_AppendFormat()
    {
        var sb = new StringBuilder(Lines * EstimatedPerLine);
        for (int i = 0; i < Lines; i++)
        {
            sb.AppendFormat("remapping {0} synonyms", i).AppendLine();
        }
        return sb.ToString(); // prevent dead-code elimination
    }

    [Benchmark(Baseline = true)]
    public string Option_C_Interpolated_AppendLine()
    {
        var sb = new StringBuilder(Lines * EstimatedPerLine);
        for (int i = 0; i < Lines; i++)
        {
            // On modern .NET, this uses the interpolated string handler => no intermediate string
            sb.AppendLine($"remapping {i} synonyms");
        }
        return sb.ToString();
    }
}