How to Safely Mix Singleton and Scoped Services with DbContext in .NET

In .NET dependency injection, combining services with different lifetimes — such as a singleton EventListener and a scoped DbContext — can cause serious runtime issues. Injecting a scoped DbContext directly into a singleton means a single database context is reused for the entire application lifetime, leading to stale data and concurrency errors. The recommended fix is to use IServiceScopeFactory inside the singleton, creating a fresh scope and a new DbContext instance for each event processed. Alternatively, the EventProcessor can be made scoped and resolved per event through the singleton listener using the same scope factory pattern. Following these best practices prevents resource misuse and ensures database operations remain isolated and thread-safe.