StringBuilder

A fast and low allocation StringBuilder for .NET.

Getting Started

Install the package:

PM> Install-Package LinkDotNet.StringBuilder

Afterward, use the package as follow:

using LinkDotNet.StringBuilder; // Namespace of the package

ValueStringBuilder stringBuilder = new ValueStringBuilder();
stringBuilder.AppendLine("Hello World");

string result = stringBuilder.ToString();

There are also smaller helper functions, which enable you to use ValueStringBuilder without any instance:

using LinkDotNet.StringBuilder;

_ = ValueStringBuilder.Concat("Hello ", "World"); // "Hello World"
_ = ValueStringBuilder.Concat("Hello", 1, 2, 3, "!"); // "Hello123!"

What does it solve?

The dotnet version of the StringBuilder is an all-purpose version that normally fits a wide variety of needs. But sometimes, low allocation is key. Therefore I created the ValueStringBuilder. It is not a class but a ref struct that tries to allocate as little as possible. If you want to know how the ValueStringBuilder works and why it uses allocations and is even faster, check out this blog post. The blog goes into a bit more in detail about how it works with a simplistic version of the ValueStringBuilder.

What it doesn't solve!

The library is not meant as a general replacement for the StringBuilder shipped with the .net framework itself. You can head over to the documentation and read about the "Known limitations". The library works best for a small to medium amount of strings (not multiple 100'000 characters, even though it can be still faster and uses fewer allocations). At any time, you can convert the ValueStringBuilder to a "normal" StringBuilder and vice versa.

The normal use case is to add concatenate strings in a hot path where the goal is to put as minimal pressure on the GC as possible.

Documentation

More detailed documentation can be found here. It is really important to understand how the ValueStringBuilder works so that you did not run into weird situations where performance/allocations can even rise.

Benchmark

The following table gives you a small comparison between the StringBuilder which is part of .NET and the ValueStringBuilder:

BenchmarkDotNet=v0.13.2, OS=macOS Monterey 12.6.1 (21G217) [Darwin 21.6.0]
Apple M1 Pro, 1 CPU, 10 logical and 10 physical cores
.NET SDK=7.0.100-rc.2.22477.23
  [Host]     : .NET 6.0.10 (6.0.1022.47605), Arm64 RyuJIT AdvSIMD
  DefaultJob : .NET 6.0.10 (6.0.1022.47605), Arm64 RyuJIT AdvSIMD


|                         Method |       Mean |    Error |   StdDev | Ratio | RatioSD |    Gen0 | Allocated | Alloc Ratio |
|------------------------------- |-----------:|---------:|---------:|------:|--------:|--------:|----------:|------------:|
|            DotNetStringBuilder |   227.3 ns |  1.31 ns |  1.22 ns |  1.00 |    0.00 |  0.7114 |    1488 B |        1.00 |
|             ValueStringBuilder |   128.7 ns |  0.57 ns |  0.53 ns |  0.57 |    0.00 |  0.2677 |     560 B |        0.38 |
| ValueStringBuilderPreAllocated |   113.9 ns |  0.67 ns |  0.60 ns |  0.50 |    0.00 |  0.2677 |     560 B |        0.38 |

For more comparison check the documentation.

Another benchmark shows that this ValueStringBuilder uses less memory when it comes to appending ValueTypes such as int, double, ...

|              Method |     Mean |    Error |   StdDev |  Gen 0 | Allocated |
|-------------------- |---------:|---------:|---------:|-------:|----------:|
| DotNetStringBuilder | 17.21 us | 0.622 us | 1.805 us | 1.5259 |      6 KB |
|  ValueStringBuilder | 16.24 us | 0.496 us | 1.462 us | 0.3357 |      1 KB |

Checkout the Benchmark for a more detailed comparison and setup.