Azure & DevOps mastery for scalable .NET applications

Azure & DevOps mastery for scalable .NET applications

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1. How different or similar are dependency injection and dependency inversion? How do you implement them?

• Dependency Inversion Principle (DIP): High-level modules should depend on abstractions, not concrete implementations.
• Dependency Injection (DI): A design pattern that fulfills DIP by injecting dependencies into classes.

In .NET:

services.AddTransient<IMyService, MyService>();

This decouples your logic, improves testability, and aligns with SOLID principles.

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2. An interface has multiple implementations. How do you manage the mapping in Program.cs?

Use factories or named registrations. For example:

services.AddTransient<IMyService, MyService1>();
services.AddTransient<IMyService, MyService2>();

Then resolve using a factory or conditional logic based on context.

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3. How do you establish DB connectivity in Entity Framework?

Configure DbContext with a connection string:

services.AddDbContext<MyDbContext>(options =>
    options.UseSqlServer(Configuration.GetConnectionString("DefaultConnection")));

This sets up EF Core to connect to SQL Server using DI.

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4. What’s the difference between DB First and Code First in EF?

Approach	Description
DB First	Start with an existing database; scaffold models
Code First	Start with C# classes; EF generates schema

Use DB First for legacy systems. Use Code First for greenfield development.

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5. How do you create a new table using Code First in EF?

Define a model and add a DbSet:

public class MyNewTable {
    public int Id { get; set; }
    public string Name { get; set; }
}

public class MyDbContext : DbContext {
    public DbSet<MyNewTable> MyNewTables { get; set; }
}

Then run:

dotnet ef migrations add AddMyNewTable
dotnet ef database update

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6. What are return types of API controllers and how do they differ?

Return Type	Framework	Description
IActionResult	ASP.NET Core	Flexible, supports multiple response types
IHttpActionResult	ASP.NET Web API	Older, used for HTTP response abstraction

Use IActionResult for modern APIs—it integrates well with filters and middleware.

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7. Is concurrency the same as asynchronous programming?

No. Concurrency is about multiple tasks running simultaneously. Asynchronous programming is about non-blocking operations.

public async Task<IActionResult> GetDataAsync() {
    var data = await _service.GetDataAsync();
    return Ok(data);
}

Async improves scalability. Concurrency improves throughput.

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8. What caching mechanisms have you used?

• In-memory caching: Fast, scoped to app instance.
• Distributed caching: Scalable, e.g., Redis.
• Output caching: For static content.

services.AddMemoryCache();
_cache.Set("key", value, TimeSpan.FromMinutes(5));

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9. How do you implement sliding expiration in caching?

var cacheEntryOptions = new MemoryCacheEntryOptions {
    SlidingExpiration = TimeSpan.FromMinutes(5)
};

_cache.Set("EmployeeDetails", employeeDetails, cacheEntryOptions);

This resets the expiration timer on each access.

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10. What’s the difference between sliding and absolute expiry?

Expiry Type	Behavior
Sliding Expiry	Resets on each access
Absolute Expiry	Expires after fixed time, regardless of access

Use sliding for frequently accessed data. Use absolute for predictable cleanup.

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11. How can you pass an array of records from EF to the database?

Use AddRange:

context.MyEntities.AddRange(myEntitiesArray);
context.SaveChanges();

Efficient for bulk inserts.

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12. What are defined tables in relation to stored procedures?

Defined tables are explicitly created in the database schema. They’re referenced in stored procedures for input/output operations and table-valued parameters.

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13. What’s clean architecture?

Clean architecture separates your app into layers:

• Domain: Core business logic
• Application: Use cases and orchestration
• Infrastructure: DB, APIs, external services

This improves testability, scalability, and maintainability.

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