🧠 Caching Query Handlers with Template Method Pattern

This project demonstrates how to implement a reusable caching mechanism for query handlers using the Template Method Pattern in .NET.

Instead of repeating cache logic in every handler, we define an abstract base class CachingDecorator<TQuery, TResponse> that:

• Checks the cache before hitting the database
• Delegates business logic to the derived handler via HandleCore
• Stores the result in cache after execution

✨ Benefits

• 🔁 Reusable caching logic
• 🧼 Clean separation of concerns
• ✅ Testable and scalable structure
• 💡 Ideal for performance-sensitive queries

📦 Technologies Used

• .NET 8
• ASP.NET Core
• IDistributedCache (In-memory)
• Minimal CQRS Setup
• Dependency Injection
• Template Method Pattern

🧪 How It Works

1. Send a query using IQueryHandler<TQuery, TResponse>.
2. CachingDecorator handles the cache check and stores result after fetching.
3. The child class (e.g. GetIWeatherForecastsQueryHandler) implements only HandleCore.

public class GetIWeatherForecastsQueryHandler 
    : CachingDecorator<GetIWeatherForecastsQuery, List<WeatherForecastViewModel>>
{
    protected override Task<List<WeatherForecastViewModel>> HandleCore(...) { ... }
}

🛠️ Run the Project

dotnet run --project WeatherForecast.Presentation

Open your browser at http://localhost:5000 or check the Swagger UI for available endpoints.

🔍 Related Design Patterns

• Template Method
• Decorator
• CQRS

📎 License

MIT

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Feel free to fork, contribute or reach out if you have ideas for improvements.
Happy coding! 🚀