https://github.com/linkdotnet/stringbuilder
A fast and low allocation StringBuilder for .NET.
https://github.com/linkdotnet/stringbuilder
csharp dotnet performance rune string string-builder stringbuilder valuestringbuilder
Last synced: about 2 months ago
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A fast and low allocation StringBuilder for .NET.
- Host: GitHub
- URL: https://github.com/linkdotnet/stringbuilder
- Owner: linkdotnet
- License: mit
- Created: 2022-04-03T15:24:50.000Z (over 3 years ago)
- Default Branch: main
- Last Pushed: 2025-05-06T07:51:36.000Z (2 months ago)
- Last Synced: 2025-05-16T08:04:47.359Z (about 2 months ago)
- Topics: csharp, dotnet, performance, rune, string, string-builder, stringbuilder, valuestringbuilder
- Language: C#
- Homepage: https://linkdotnet.github.io/StringBuilder/
- Size: 946 KB
- Stars: 100
- Watchers: 3
- Forks: 10
- Open Issues: 2
-
Metadata Files:
- Readme: README.md
- Changelog: CHANGELOG.md
- License: LICENSE
Awesome Lists containing this project
README
# StringBuilder
[](https://github.com/linkdotnet/StringBuilder/actions/workflows/dotnet.yml)
[](https://www.nuget.org/packages/LinkDotNet.StringBuilder/)
[](https://github.com/linkdotnet/StringBuilder/releases)
A fast and low allocation StringBuilder for .NET.
## Getting Started
Install the package:
> PM> Install-Package LinkDotNet.StringBuilder
Afterward, use the package as follow:
```csharp
using LinkDotNet.StringBuilder; // Namespace of the package
using ValueStringBuilder stringBuilder = new();
stringBuilder.AppendLine("Hello World");
string result = stringBuilder.ToString();
```
There are also smaller helper functions, which enable you to use `ValueStringBuilder` without any instance:
```csharp
string result1 = ValueStringBuilder.Concat("Hello ", "World"); // "Hello World"
string result2 = ValueStringBuilder.Concat("Hello", 1, 2, 3, "!"); // "Hello123!"
```
By default, `ValueStringBuilder` uses a rented buffer from `ArrayPool.Shared`.
You can avoid renting overhead with an initially stack-allocated buffer:
```csharp
using ValueStringBuilder stringBuilder = new(stackalloc char[128]);
```
Note that this will prevent you from returning `stringBuilder` or assigning it to an `out` parameter.
## 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](https://steven-giesel.com/blogPost/4cada9a7-c462-4133-ad7f-e8b671987896) blog post.
The blog goes into a bit more in detail about how it works with a simplistic version of the `ValueStringBuilder`.
## What doesn't it solve?
The library is not meant as a general replacement for the `StringBuilder` built into .NET. You can head over to the documentation and read about the ["Known limitations"](https://linkdotnet.github.io/StringBuilder/articles/known_limitations.html).
The library works best for a small to medium length strings (not hundreds of thousands of characters, even though it can be still faster and performs fewer allocations). At any time, you can convert the `ValueStringBuilder` to a "normal" `StringBuilder` and vice versa.
The normal use case is to 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](https://linkdotnet.github.io/StringBuilder). 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 compares the built-in `StringBuilder` and this library's `ValueStringBuilder`:
```no-class
BenchmarkDotNet v0.14.0, macOS Sequoia 15.3.1 (24D70) [Darwin 24.3.0]
Apple M2 Pro, 1 CPU, 12 logical and 12 physical cores
.NET SDK 9.0.200
[Host] : .NET 9.0.2 (9.0.225.6610), Arm64 RyuJIT AdvSIMD
DefaultJob : .NET 9.0.2 (9.0.225.6610), Arm64 RyuJIT AdvSIMD
| Method | Mean | Error | StdDev | Ratio | Gen0 | Allocated | Alloc Ratio |
|-------------------- |----------:|---------:|---------:|------:|-------:|----------:|------------:|
| DotNetStringBuilder | 126.74 ns | 0.714 ns | 0.667 ns | 1.00 | 0.1779 | 1488 B | 1.00 |
| ValueStringBuilder | 95.69 ns | 0.118 ns | 0.110 ns | 0.76 | 0.0669 | 560 B | 0.38 |
```
For more comparisons, check the documentation.
Another benchmark shows that `ValueStringBuilder` allocates less memory when appending value types (such as `int` and `double`):
```no-class
| Method | Mean | Error | StdDev | Gen0 | Gen1 | Allocated |
|------------------------------- |---------:|--------:|--------:|-------:|-------:|----------:|
| ValueStringBuilderAppendFormat | 821.7 ns | 1.29 ns | 1.14 ns | 0.4330 | - | 3.54 KB |
| StringBuilderAppendFormat | 741.5 ns | 5.58 ns | 5.22 ns | 0.9909 | 0.0057 | 8.1 KB |
```
Check out the [Benchmark](tests/LinkDotNet.StringBuilder.Benchmarks) for a more detailed comparison and setup.
## Support & Contributing
Thanks to all [contributors](https://github.com/linkdotnet/StringBuilder/graphs/contributors) and people that are creating bug-reports and valuable input:
