Topic 20112 min readStructured Tutorial

ASP.NET Core Interview Preparation Questions

Quick Answer

ASP.NET Core is a cross-platform, high-performance framework for building modern web applications. Key interview topics include middleware, dependency injection, routing, configuration, and security. Understanding these concepts with practical examples will help you excel in ASP.NET Core interviews.

Learning Objectives

Explain the purpose of ASP.NET Core Questions in a practical learning context.
Identify the main ideas, terms, and decisions involved in ASP.NET Core Questions.
Apply ASP.NET Core Questions in a simple real-world scenario or practice task.

Introduction to ASP.NET Core Interview Preparation

ASP.NET Core is a popular framework for building scalable and high-performance web applications. Preparing for an interview requires understanding its core concepts and practical usage.

This tutorial covers common ASP.NET Core interview questions, explanations, and examples to help you confidently answer technical queries.

Build modern, cloud-ready, internet-connected applications.

Understanding ASP.NET Core Basics

ASP.NET Core is a redesign of ASP.NET, optimized for modern web development. It supports cross-platform deployment and modular architecture.

Key features include middleware pipeline, dependency injection, and built-in support for configuration and logging.

Cross-platform support (Windows, Linux, macOS)
Unified MVC and Web API frameworks
Lightweight and modular design
Built-in dependency injection

Middleware in ASP.NET Core

Middleware components form a pipeline to handle HTTP requests and responses. Each middleware can perform actions before and after the next component in the pipeline.

Request processing pipeline
Custom middleware creation
Order of middleware matters

Dependency Injection (DI)

ASP.NET Core has built-in support for dependency injection, promoting loose coupling and easier testing.

Services registered in Startup.cs
Scoped, Transient, and Singleton lifetimes
Constructor injection is common

Routing and Configuration

Routing in ASP.NET Core maps incoming requests to controller actions or Razor pages. It supports attribute routing and conventional routing.

Configuration is flexible, supporting JSON, environment variables, command-line arguments, and more.

Use of UseRouting and UseEndpoints middleware
Route templates and constraints
Configuration providers and options pattern

Security in ASP.NET Core

Security is critical in web applications. ASP.NET Core supports authentication, authorization, and data protection.

Authentication schemes (Cookie, JWT, OAuth)
Role-based and policy-based authorization
Data protection APIs

Practical Example

This middleware writes messages before and after the next component in the pipeline.

This registers a service with transient lifetime for dependency injection.

Examples

Simple Middleware Example

public class CustomMiddleware
{
    private readonly RequestDelegate _next;
    public CustomMiddleware(RequestDelegate next) { _next = next; }
    public async Task InvokeAsync(HttpContext context)
    {
        // Logic before next middleware
        await context.Response.WriteAsync("Middleware executing before next component.\n");
        await _next(context);
        // Logic after next middleware
        await context.Response.WriteAsync("Middleware executing after next component.\n");
    }
}

This middleware writes messages before and after the next component in the pipeline.

Registering Services with Dependency Injection

public void ConfigureServices(IServiceCollection services)
{
    services.AddTransient<IMyService, MyService>();
}

This registers a service with transient lifetime for dependency injection.

Best Practices

Understand the middleware pipeline order and its impact on request processing.
Use dependency injection to manage service lifetimes effectively.
Apply attribute routing for clearer and maintainable route definitions.
Secure your application using built-in authentication and authorization features.
Use configuration providers to manage environment-specific settings.

Common Mistakes

Ignoring middleware order, causing unexpected behavior.
Registering services with incorrect lifetimes leading to resource leaks or concurrency issues.
Hardcoding configuration values instead of using configuration providers.
Neglecting security best practices such as proper authentication and authorization.
Not handling exceptions properly in middleware.

Hands-on Exercise

Create Custom Middleware

Write a middleware that logs the request path and response status code.

Expected output: Middleware logs request path and response status code to the console or a file.

Hint: Use HttpContext.Request.Path and HttpContext.Response.StatusCode properties.

Implement Dependency Injection

Expected output: Controller receives the service instance via constructor injection.

Hint: Use services.AddScoped<TInterface, TImplementation>() in ConfigureServices.

Interview Questions

What is middleware in ASP.NET Core?

Interview

Middleware is software assembled into an application pipeline to handle requests and responses. Each component can perform operations before and after the next component.

How does dependency injection work in ASP.NET Core?

Interview

ASP.NET Core has built-in dependency injection where services are registered with lifetimes (Transient, Scoped, Singleton) and injected into constructors where needed.

What are the differences between Scoped, Transient, and Singleton service lifetimes?

Interview

Transient services are created each time requested, Scoped services are created per client request, and Singleton services are created once and shared throughout the application.

How do you secure an ASP.NET Core application?

Interview

By implementing authentication schemes like cookies or JWT, using authorization policies, and protecting data with built-in APIs.