TL;DR: Micro-optimizations are not a substitute for design work. They are how you earn the right to redesign. In the Azure Service Bus SDK, repeated work in the Body property first led to smaller allocation fixes. Once those fixes exposed the shape of the problem, a small internal redesign made the code faster, clearer, and easier to reason about. “This code is bad. We should rewrite it.” Most developers have heard that sentence. Many have said it. I have too. The problem is not...
TL;DR: After temporary allocations were removed from the Azure Event Hubs partition-key encoding path, the Jenkins lookup3 hash loop itself became the next interesting place to look. Tightening that loop reduced CPU overhead, but it also raised the bar for review, portability, and correctness. I like performance work most when it starts with a boring question: why is this small method showing up so much? That question came up while looking at the Azure Event Hubs client. Event Hubs is built for...
TL;DR: Small code paths become expensive when cloud workloads execute them millions of times. The Azure Event Hubs partition key resolver is one of those paths. By removing temporary allocations from the partition-key encoding path, the Azure Event Hubs SDK reduced garbage collection pressure on a publishing hot path. I like performance work most when it starts with a boring question: why is this small method showing up so much? That question came up while looking at the Azure Event Hubs client...
One of the great features of .NET is that you can mix its programming languages (C#, F#, VB.NET) in a single solution and that assemblies written in one language can call assemblies written in other languages. This is great, especially when starting with F#. A team does not need to switch everything at once, but can keep using the existing C# code and use Interop to call C# from F# or vice versa.In this article, we take a look at the Interop story in 2026. Spoilers: it works great.
Yesterday evening, I gave a workshop titled “To test, or not to test” at the Software Crafters Zürich Meetup. In the workshop, we gathered reasons to write tests: being confident that the code works, being confident that regressions can be prevented, helping to drive the implementation, and having documentation of the system. Interestingly, when I prepared the workshop, I forgot about the documentation aspect of the tests. Here is why and why it matters.
I was invited by JetBrains to talk about OOP and FP and how C# and F# support these paradigms.
Here, you can find the Recording.
And here are the slides.
Happy combining of OOP and FP in your code!
Most code running on .Net is written in C#. So when you consider writing some code in F#, you probably already have a good amount of C# code. C# code you want to keep. It probably doesn’t make economic sense to port C# code to F#.
The good news is that you can start using F# anyway. F# and C# have excellent interoperability.
Just today, I read on a social media platform that the author doesn’t like that most programming languages incorporate more and more functional features. The post was accompanied by a short example of pattern matching in C# using some of the features introduced in the latest updates. More generally, I hear and read repeatedly from people that tried to write code in a more functional programming style in C# but weren’t happy with the resulting code. The code was just too hard to read...
A myth about F# that I hear repeatedly is that imperative code (e.g. loops) is simpler than functional code (e.g. folds). On one hand, simplicity is very subjective. On the other hand, simplicity is mostly determined by familiarity.
A typically used example is something like the following:
Simple:
Difficult:
Let’s see what’s wrong with this myth.
Sometimes when I talk to C# developers about F#, they say they don’t want to switch to a functional programming language. When I reply that F# is my favourite object-oriented programming language, they look a bit puzzled. They typically think that F# is for functional programming, while C# is for object-oriented programming. And this is wrong!