Event Sourcing with .NET and Marten

The year 2026 began with unusually heavy snowfall in the Netherlands. It was more than we are used to, and in some cases enough to cause buildings to collapse.

I work for an organization that provides Building Information Management services, so it made me think: what happens after a building collapses? There will probably be investigations into the specifications that were used at the time. Do we keep the full history? Do we know whether changes were made, why they were made, when they were made, and by whom?

I had already been looking for a reason to dive into event sourcing, and this felt like a useful example. Event sourcing is not only about storing the current state of something, but about storing the facts that led to that state. That makes it a good fit for systems where history matters.

In this post, I’ll use changing roof specifications as a small example to explain event sourcing, and show how it can be implemented in .NET with Marten.

Whole Team Collaboration: Navigating the seven C's

On November 27 and 28, I went to the XP Days Benelux conference. This blog post is a short recap of all the things I learned.

In this third post in the XP Days series, I’m sharing my notes and reflections from the session “Whole Team Collaboration: Navigating the Seven C’s” by Per Beining. There are many ways of working together, and many ways of not really working together. By introducing the Seven C’s (spoiler: there are actually eight), Per offered a simple but powerful lens to help teams recognise how they currently collaborate and what they might change to truly work together.

The goal of the session was to build awareness: understand the difference between merely working side by side and genuinely collaborating, and learn how to spot which “C” your team is currently navigating—so you can steer toward the harbour you actually want to reach.

DUO Portfolio Game

On November 27 and 28, I went to the XP Days Benelux conference. This blog post is a short recap of all the things I learned.

In this second post, I’m sharing my notes and reflections from the session “DUO Portfolio Game” by Jan-Willem Zijlstra, Jeroen Smit, and Willem Kleinenberg. The session introduced a game they developed to spark conversations about culture, collaboration, and ways of working. Through several rounds, participants experienced firsthand how different strategies for distributing work across teams can shape flow, ownership, and alignment.

The goal of the session was clear: explore how teams might organize and collaborate more effectively, and discover what happens when you shift constraints, responsibilities, or communication paths.

So long, and thanks for all the fish - The farewell tour

On November 27 and 28, I went to the XP Days Benelux conference. This blog post is a short recap of all the things I learned.

In this first post, I’m sharing my notes and reflections from the session “So Long, and thanks for all the fish - The farewell tour" by Ron Eringa, Paul Kuijten, and Dajo Breddels. The session explored the question of whether the Agile movement has run its course: been there, done that, got the T-shirt. With the Agile label losing some of its shine, the facilitators invited us to properly say goodbye to what no longer serves us, and to salvage the practices and principles still worth keeping.

The goal of the session was simple but important: take stock. Is Agile dead? And if not, how do we move forward?

An Astronaut's Guide to Life on Earth

Colonel Chris Hadfield has spent decades training as an astronaut and has logged nearly 4000 hours in space. During this time he has broken into a Space Station with a Swiss army knife, disposed of a live snake while piloting a plane, and been temporarily blinded while clinging to the exterior of an orbiting spacecraft. The secret to Col. Hadfield’s success-and survival-is an unconventional philosophy he learned at NASA: prepare for the worst-and enjoy every moment of it.