An Introduction to writing high performance C# code

Writing high-performance C# code is a skill that can benefit any .NET developer. High-performance code can run faster, consume less memory, and scale better. Here are some tips and resources to get you started:

• Choose your data types carefully. Different data types have different performance characteristics, such as size, allocation, boxing, and casting. For example, using int instead of long when possible can save memory and improve speed. Using struct instead of class can avoid heap allocations and reduce garbage collection pressure¹.
• Use for loops instead of foreach loops. foreach loops can cause hidden allocations and boxing when iterating over collections that are not generic or implement IEnumerable<T>for loops can avoid these overheads and give you more control over the iteration logic¹.
• Use StringBuilder for string concatenation. Strings are immutable in C#, which means every time you modify a string, a new string object is created and the old one is discarded. This can cause a lot of memory allocations and garbage collectionStringBuilder is a mutable class that can append strings without creating new objects¹.
• Use Span<T> and Memory<T> for efficient data processing. These are new types introduced in C# 7.2 and .NET Core 2.1 that allow you to access and manipulate data without copying or allocating memory. They can be used to process arrays, strings, streams, buffers, and other data sources with minimal overhead²³.
• Use the new high-performance JSON APIs. In .NET Core 3.0, Microsoft introduced a new set of APIs for working with JSON data, such as System.Text.Json, JsonDocument, and Utf8JsonWriter. These APIs are designed to be fast, lightweight, and low-allocation, compared to the older Newtonsoft.Json library²⁴.
• Measure your code performance using benchmarks and profilers. The best way to know if your code is performant is to measure it using tools that can provide accurate and reliable results. Benchmark.NET is a popular library for writing and running micro-benchmarks in C#. JetBrains dotMemory is a powerful profiler that can help you analyze the memory usage and allocations of your .NET applications²³.

These are just some of the tips and resources that can help you write high-performance C# code. There are many more topics and techniques that you can explore, such as parallelism, concurrency, async/await, I/O pipelines, array pools, etc. The key is to always use a data-driven approach, focus on the hot paths of your code, and apply the best practices that suit your scenario.

I hope this blog post was helpful to you. If you want to learn more about writing high-performance C# code, I recommend checking out the following links:

¹: https://www.c-sharpcorner.com/UploadFile/dacca2/5-tips-to-improve-performance-of-C-Sharp-code/ 

²: https://www.jetbrains.com/dotnet/guide/tutorials/dotnet-days-online-2021/turbocharged-writing-high-performance-csharp-and-net-code/ 

³: https://www.stevejgordon.co.uk/writing-high-performance-csharp-and-dotnet-code

 ⁴: https://github.com/PacktPublishing/High-Performance-Programming-in-C-Sharp-and-.NET 

⁵: https://stackoverflow.com/questions/183033/improve-speed-performances-in-c-sharp