What is IOptions<T> pattern in configuration?
💡 Concept: IOptions<T> Pattern
IOptions<T> is a pattern in ASP.NET Core for accessing strongly typed configuration settings.
📘 Quick Intro
This pattern simplifies accessing configuration sections and provides type safety.
🧠 Analogy
Like having a typed settings object you can inject wherever needed, rather than reading raw config repeatedly.
🔧 Technical Explanation
- Bind configuration sections to POCO classes.
- Register with services.Configure<T> in Startup.cs or Program.cs.
- Inject IOptions<T> into dependent classes.
- Supports reload-on-change and validation.
- Promotes separation of concerns and testability.
🎯 Use Cases
- ✅ Accessing appsettings.json sections as strongly typed objects.
- ✅ Injecting configuration into services and controllers.
- ✅ Supporting configuration reload on changes.
- ✅ Enforcing validation on config data.
💻 Code Example
// POCO class for config
public class MySettings {
public string ApiKey { get; set; }
public int Timeout { get; set; }
}
// Register in Startup.cs or Program.cs
services.Configure<MySettings>(Configuration.GetSection(""MySettings""));
// Inject and use in a service
public class MyService {
private readonly MySettings _settings;
public MyService(IOptions<MySettings> options) {
_settings = options.Value;
}
}
❓ Interview Q&A
Q1: What is IOptions<T>?
A: Interface for accessing strongly typed config settings.
Q2: How do you register IOptions<T>?
A: Using services.Configure<T> method.
Q3: Can IOptions support reload-on-change?
A: Yes.
Q4: What is the advantage of IOptions pattern?
A: Type safety and separation of concerns.
Q5: How do you inject configuration into classes?
A: Via IOptions<T> in constructor.
Q6: Can you validate config with IOptions?
A: Yes, with validation extensions.
Q7: Is IOptions pattern specific to ASP.NET Core?
A: Yes.
Q8: Can IOptions be used with POCOs?
A: Yes.
Q9: How is IOptions different from IConfiguration?
A: IOptions provides strongly typed access; IConfiguration is key-value.
Q10: What namespace contains IOptions?
A: Microsoft.Extensions.Options.
📝 MCQs
Q1. What is IOptions<T>?
- Interface for strongly typed config
- Generic interface
- Configuration key
- Service provider
Q2. How do you register IOptions<T>?
- services.AddOptions
- services.Configure<T>
- services.AddSingleton
- services.AddTransient
Q3. Can IOptions support reload-on-change?
- No
- Yes
- Sometimes
- Never
Q4. Advantage of IOptions pattern?
- Speed
- Type safety
- Memory
- Security
Q5. How to inject configuration?
- Via constructor
- Via properties
- Via method
- Manual lookup
Q6. Can config be validated?
- No
- Yes
- Sometimes
- Rarely
Q7. Is IOptions specific to ASP.NET Core?
- No
- Yes
- Sometimes
- Rarely
Q8. Can IOptions be used with POCOs?
- No
- Yes
- Sometimes
- Never
Q9. Difference between IOptions and IConfiguration?
- Strongly typed vs key-value
- Both same
- Only IConfiguration
- Only IOptions
Q10. IOptions namespace?
- System.Configuration
- Microsoft.Extensions.Options
- Microsoft.AspNetCore
- System.Options
💡 Bonus Insight
The IOptions<T> pattern promotes clean configuration management and improves code maintainability.
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