ObserverPatternExamples - Observer Design Pattern in C#

This solution demonstrates three different implementations of the Observer design pattern in C# and .NET, showing the evolution from a traditional interface-based approach to modern reactive programming. Each project in the solution tackles the same problem — notifying subscribers of events — using a progressively more sophisticated technique.

The first project, ApiBasedObserverExample, implements the classic Gang of Four Observer pattern with manual subscription management using IObserver and Observable classes. The second project, EventBasedObserverExample, leverages C#'s native event system with delegates and EventHandler<T> for a more idiomatic approach. The third project, RxNetObserverExample, uses Reactive Extensions (Rx.NET) with IObservable<T> and IObserver<T> interfaces, enabling composable, scalable reactive streams.

Together, these examples provide a comprehensive comparison of observer pattern strategies in .NET, helping developers understand the trade-offs between simplicity, language integration, and scalability when implementing event-driven architectures.

Getting Started

Prerequisites

• .NET 7.0 SDK or later
• An IDE such as Visual Studio, Visual Studio Code, or JetBrains Rider

Running the Project

# Run the classic API-based observer example
dotnet run --project ApiBasedObserverExample

# Run the event-based observer example
dotnet run --project EventBasedObserverExample

# Run the Rx.NET observer example
dotnet run --project RxNetObserverExample

Related Resources

Blog Articles

• Observer Design Pattern in C# - How to Simplify Event-Driven Programming

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