Back to Simplicity: Why We Built CALM, a Lock-Free Single-Thread Messaging Library for .NET

Hello everyone! For many years, I have been developing equipment control software and long-term support products using .NET/C#. Based on the experiences gained through working with various development teams, I would like to talk about why I created CALM (Cooperative Async Lock-free Messaging) , an open-source library for .NET. The Magic of UI Thread + Event-Driven + async/await My journey with .NET/C# began around the days of .NET Framework 4.0. At the time, code-behind in Windows Forms was incredibly intuitive. It allowed me to join the development team and become productive in a very short period. Back then, executing time-consuming operations on a separate thread and returning the results to the UI thread via callbacks was painful and error-prone. However, the introduction of async/await in .NET Framework 4.5 completely shifted the paradigm. The SynchronizationContext magically handled thread marshaling behind the scenes, and our code became amazingly simple. "Running asynchronous operations safely on a single thread (the UI thread) via an event-driven approach" — this seamless developer experience was my starting point. Divide and Conquer, Dependency Management, and CQS As our product evolved, the codebase grew, and the development team expanded beyond a certain size. Suddenly, the software became exponentially complex. Following industry best practices, we introduced MVP and MVVM patterns to separate the UI from the business logic. We also refactored our domain models based on Domain-Driven Design (DDD) and Clean Architecture principles, alignment with the team's domain knowledge. While this helped organize the logic within individual models, it introduced a new nightmare: complex dependencies between models. We struggled heavily with initialization, especially with models that had circular or mutual dependencies. To break this web of tight coupling, we introduced a mechanism that combined the Observer pattern (inspired by Android's EventBus) with the philosoph