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.
In our product, I sometimes encounter the problem of dynamic IN-lists in SQL. First, they appear harmless, but soon they lead to an unnecessary amount of query plans. In this blog post I share how to circumvent those issues with TVP. A clean, performant and reusable way to solve this problem!
Not having to annotate types for every argument and return value in F# is a big relief. In this blog post, I share some tips and tricks to reduce the need for type annotations.
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.
Welcome to our team! Today is your first day, which means it’s the day you’ll release your first feature. You’ll see everything needed to design, implement, and release a feature in our system. We’ll touch on F# language features, our TDD style, and some architecture topics.
This blog post is part of the F# Advent Calendar 2024 (thanks, Sergey, for the organisation).
Bi-temporal event sourcing combines storing data as a sequence of events, which tell what has happened with the data, and the data has two associated points of time, one when the data entered the system and one when the data takes effect. This post is about our 8+ years of experience with bi-temporal event sourcing, along with code samples showing how to achieve this. Feel free to skip the code blocks and just read the conceptual parts. But you’ll miss the beauty of F# 😂 This post is part...
After one of my presentations about F#, we had a discussion about the effect of type inference, resulting in almost no type annotations, on code readability and reviewability. The concern was that it makes the code harder to understand, especially when reviewing code, for example, outside of an IDE (GitHub/Azure DevOps/… Pull Requests).
So is there a problem or not? Let’s see.
Yesterday, I found myself face-to-face with a rather peculiar phenomenon that managed to consume a good hour of my time. As is often the case, the solution turned out to be surprisingly simple. With the intention of documenting this for future reference (especially for my future self), I am writing this short blog post. What happened? A colleague of mine updated XUnit in our solution and merged it into our main branch. When I pulled the new code locally and tried to restore the NuGet packages...
Sometimes, unit tests are really small – so small that they fit on a single line:
In F#, you specify the order of files explicitly. Any code can only reference types, modules and functions that are higher up in the same file or in a file higher up in the file list. When starting with F#, this feels strange because most programming languages don’t rely on ordered files. Some call this feature even dumb.