Angular Dependency Injection Simplified for .Net and Java Developers

Angular's dependency injection (DI) differs from .NET and Java because TypeScript interfaces are erased at compile time and don't exist in the resulting JavaScript. This means Angular uses classes as DI tokens instead of interfaces. Despite injecting a class directly, Angular still provides true DI — you can swap implementations without changing consumer code by using the `provide`/`useClass` pattern in the module providers array. Extending the original service class and registering the new one as a replacement allows partial method overrides while inheriting the rest.