The Event Aggregator Pattern in .NET MAUI: Building Loosely Coupled Communication
As a MAUI app grows, ViewModels referencing each other directly turns into architectural debt that’s hard to test and maintain. This post introduces the Event Aggregator pattern — a centralized messaging hub that lets components communicate without knowing about one another.
What you’ll learn
- Why tight coupling between ViewModels, services, and navigation causes hidden ripple effects
- How to build an Event Aggregator from scratch: defining events, an
IEventAggregatorinterface, a minimal implementation, and registering it in DI - Publishing and subscribing to strongly-typed events so ViewModels stay fully decoupled
- Why it fits MAUI’s short-lived pages and changing navigation stacks especially well
- Critical considerations: avoiding memory leaks via unsubscribe/weak references, marshalling handlers back to the MainThread, and not overusing events
- How it compares to the deprecated
MessagingCenter, and how it makes unit testing simple to mock
A solid pattern to keep growing MAUI codebases modular and maintainable.