Refactoring Legacy C# Code: Issues with Inherited Interfaces and Dependency Injection
Hey everyone, I'm running into an issue that's driving me crazy... I tried several approaches but none seem to work. I'm working on a personal project and I'm sure I'm missing something obvious here, but Currently refactoring some legacy code that heavily relies on interfaces that have become convoluted over time... I’m facing a challenge with an interface `IService` that has been implemented in multiple classes, but now needs to support Dependency Injection (DI) without breaking existing functionality. Here’s a simplified version of the interface and its implementations: ```csharp public interface IService { void Execute(); } public class LegacyService : IService { public void Execute() { // Legacy code execution } } public class NewService : IService { public void Execute() { // New logic execution } } ``` In my startup configuration, I’m trying to register these services: ```csharp services.AddSingleton<IService, LegacyService>(); // Later I want to switch to NewService without much hassle ``` The challenge arises when I attempt to switch to `NewService`. While testing, I encountered an error: `InvalidOperationException: Unable to resolve service for type 'IService' while attempting to activate 'NewService'`. It seems that during initialization, the DI container can’t find the appropriate mapping for `IService`. I’ve tried multiple approaches, such as using `AddTransient` and `AddScoped`, but the issue persists. To add to the confusion, I noticed that some parts of the application still refer to `LegacyService` directly rather than through the interface. This leads to tight coupling which I’m trying to avoid. To maintain functionality while transitioning to the new service, I’d like to ensure that all references to `IService` are updated without causing any disruption. The ultimate goal is to introduce `NewService` gradually, ensuring that the legacy logic can still operate until we fully phase it out. What strategies could I employ to refactor this code effectively? Are there best practices to manage interface implementations in a DI context, especially with legacy systems? Any insights would be greatly appreciated! This is part of a larger service I'm building. What's the best practice here? My development environment is Ubuntu. Has anyone else encountered this? I'm working with C# in a Docker container on Ubuntu 22.04. Any feedback is welcome! For reference, this is a production CLI tool. Has anyone else encountered this?