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How do you register and resolve a service using ASP.NET Core's built-in dependency injection container? What is the difference between Singleton, Scoped, and Transient service lifetimes in ASP.NET Core's DI container? What is the Inversion of Control (IoC) principle, and how does dependency injection relate to it as one specific technique? How does constructor injection differ from property (setter) injection, and why is constructor injection generally preferred? How would you implement the Factory pattern using dependency injection to resolve a specific implementation at runtime based on a parameter, when the standard container can't decide statically? How do you correctly and safely resolve a Scoped service from within a Singleton service using IServiceScopeFactory, avoiding the captive dependency problem? How would you write a custom IServiceProviderFactory or use a third-party container (like Autofac) to enable advanced DI features not supported by the built-in ASP.NET Core container, like property injection or convention-based registration? How does the DI container resolve a class with MULTIPLE constructors, and how do you influence which one gets chosen?
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C# › Dependency Injection & IoC Principles

What causes a 'captive dependency' bug, and how does ASP.NET Core's DI container detect and prevent it?

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Answer

A captive dependency occurs when a longer-lived service (like Singleton) injects a shorter-lived one (like Scoped) — the Scoped instance gets 'captured' and effectively lives as long as the Singleton, defeating its intended per-request lifecycle and potentially causing stale data or thread-safety issues; ASP.NET Core's DI container detects this specific misconfiguration and throws an exception at service resolution time by default (with scope validation enabled).
builder.Services.AddSingleton<ICacheService, CacheService>();
builder.Services.AddScoped<IDbContext, AppDbContext>();

public class CacheService : ICacheService {
  public CacheService(IDbContext db) { } // Error at startup: captive dependency detected!
}
Real-world example Debugging a subtle production bug where a database context was unexpectedly shared and stale across multiple unrelated requests.

Common follow-ups: How would you correctly restructure a Singleton that genuinely needs access to Scoped services on demand, using IServiceScopeFactory?

Memory & Garbage Collection
All 10 Dependency Injection & IoC Principles questions