ASP.NET Core Interview Questions

ASP.NET Core is an open-source, cross-platform framework developed by Microsoft for building modern, high-performance web applications and services. It is a modular and lightweight framework that enables developers to create robust and scalable applications that can run on Windows, Linux, and macOS. ASP.NET Core supports a wide range of programming languages, including C#, F#, and Visual Basic, allowing developers to choose the language that best suits their preferences and requirements.

One of the key features of ASP.NET Core is its flexibility and modularity. It allows developers to use only the components they need, reducing the overall footprint of the application and improving performance. ASP.NET Core also embraces modern web development practices, providing support for dependency injection, middleware components, and a unified programming model for building both web APIs and web applications. With its cross-platform compatibility, high performance, and developer-friendly features, ASP.NET Core has become a popular choice for building modern, scalable, and cross-platform web applications.

ASP.NET Core Interview Questions For Freshers

1. What is ASP.NET Core?

ASP.NET Core is an open-source, cross-platform framework developed by Microsoft for building modern, high-performance web applications and services.

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.Hosting;

class Program
{
    static void Main()
    {
        CreateHostBuilder().Build().Run();
    }

    public static IHostBuilder CreateHostBuilder() =>
        Host.CreateDefaultBuilder()
            .ConfigureWebHostDefaults(webBuilder =>
            {
                webBuilder.UseStartup<Startup>();
            });
}

public class Startup
{
    public void Configure(IApplicationBuilder app)
    {
        app.Run(async (context) =>
        {
            await context.Response.WriteAsync("Hello, World!");
        });
    }
}

2. Explain the key features of ASP.NET Core?

Key features include cross-platform support, modularity, flexibility, high performance, and support for modern web development practices.

3. What is the difference between ASP.NET and ASP.NET Core?

ASP.NET Core is cross-platform and supports modular, lightweight architecture, while ASP.NET is primarily designed for Windows and follows a more monolithic structure.

4. What is Dependency Injection in ASP.NET Core?

Dependency Injection is a design pattern in ASP.NET Core that allows the application to be loosely coupled by injecting dependencies into components instead of hardcoding them.

5. Explain Middleware in ASP.NET Core?

Middleware components are software components that are used to process requests and responses in the ASP.NET Core pipeline. They can perform tasks such as authentication, logging, and error handling.

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.DependencyInjection;

class Startup
{
    public void Configure(IApplicationBuilder app)
    {
        // Use middleware to handle requests and respond
        app.Use(async (context, next) =>
        {
            // Execute logic before the next middleware
            await context.Response.WriteAsync("Executing Middleware 1\n");

            // Call the next middleware in the pipeline
            await next();

            // Execute logic after the next middleware
            await context.Response.WriteAsync("Executing Middleware 1 Again\n");
        });

        // Use another middleware in the pipeline
        app.Use(async (context, next) =>
        {
            await context.Response.WriteAsync("Executing Middleware 2\n");
            await next();
        });

        // Use a terminal middleware to generate the final response
        app.Run(async (context) =>
        {
            await context.Response.WriteAsync("Hello, World!");
        });
    }
}

6. What is Razor Pages in ASP.NET Core?

Razor Pages is a feature in ASP.NET Core that makes it easier to build web pages using a page-focused approach with the Razor view engine.

7. Explain the concept of Tag Helpers?

Tag Helpers in ASP.NET Core are a way to create reusable HTML components with server-side logic, making it easier to work with server-side code in views.

8. What is the purpose of the ConfigureServices method in Startup.cs?

ConfigureServices is used to configure services such as dependency injection and is called by the runtime when the application starts.

9. Differentiate between TempData, ViewData, and ViewBag?

TempData persists data between requests, ViewData is used to pass data from the controller to the view, and ViewBag is a dynamic property of the controller used for the same purpose.

10. What is the purpose of the appsettings.json file in ASP.NET Core?

appsettings.json is used to store configuration settings for an ASP.NET Core application.

11. Explain Entity Framework Core and its role in ASP.NET Core?

Entity Framework Core is an Object-Relational Mapping (ORM) framework used for database access in ASP.NET Core applications, providing a convenient way to work with databases using C#.

12. What is the purpose of the ASP.NET Core Startup class?

The Startup class in ASP.NET Core is used to configure the application, set up services, and define the request processing pipeline.

13. How does ASP.NET Core support cross-platform development?

ASP.NET Core is designed to be cross-platform, allowing developers to build and run applications on Windows, Linux, and macOS.

14. What is Kestrel in the context of ASP.NET Core?

Kestrel is a lightweight, cross-platform web server that is used as the default web server in ASP.NET Core applications.

15. Explain the role of the wwwroot folder?

The wwwroot folder is used to store static files, such as HTML, CSS, and JavaScript, that are served directly to the client without going through the ASP.NET Core pipeline.

<!-- Example HTML file referencing a CSS file from the wwwroot folder -->
<!DOCTYPE html>
<html>
<head>
    <title>Static File Example</title>
    <link rel="stylesheet" href="/css/styles.css">
</head>
<body>
    <h1>Hello, World!</h1>
</body>
</html>

16. What is the purpose of the IActionResult interface?

IActionResult is an interface that represents the result of an action method in ASP.NET Core. It allows for different types of responses, such as views, redirects, or JSON data.

17. What is the use of the [Authorize] attribute in ASP.NET Core?

The [Authorize] attribute is used to restrict access to a controller or action method to only authenticated users.

18. Explain Cross-Origin Resource Sharing (CORS) in ASP.NET Core?

CORS is a security feature that controls how web pages in one domain can request and consume resources from another domain. ASP.NET Core provides middleware to configure CORS policies.

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;

public class Startup
{
    public Startup(IConfiguration configuration)
    {
        Configuration = configuration;
    }

    public IConfiguration Configuration { get; }

    public void ConfigureServices(IServiceCollection services)
    {
        services.AddCors(options =>
        {
            options.AddPolicy("AllowSpecificOrigin",
                builder => builder.WithOrigins("http://example.com")
                                  .AllowAnyMethod()
                                  .AllowAnyHeader());
        });

        // Other service configurations...
    }

    public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
    {
        if (env.IsDevelopment())
        {
            app.UseDeveloperExceptionPage();
        }
        else
        {
            app.UseExceptionHandler("/Home/Error");
            app.UseHsts();
        }

        // Enable CORS
        app.UseCors("AllowSpecificOrigin");

        app.UseHttpsRedirection();
        app.UseStaticFiles();

        app.UseRouting();

        app.UseAuthorization();

        app.UseEndpoints(endpoints =>
        {
            endpoints.MapControllerRoute(
                name: "default",
                pattern: "{controller=Home}/{action=Index}/{id?}");
        });
    }
}

19. What is the purpose of the ConfigureServices method in Startup.cs?

ConfigureServices is used to configure services such as dependency injection and is called by the runtime when the application starts.

20. What is the role of the app.UseExceptionHandler middleware?

app.UseExceptionHandler is used to handle exceptions globally in an ASP.NET Core application, providing a centralized way to log and handle errors.

21. How can you enable Cross-Site Request Forgery (CSRF) protection in ASP.NET Core?

CSRF protection in ASP.NET Core is enabled by using the [ValidateAntiForgeryToken] attribute and generating anti-forgery tokens in forms.

22. Explain the purpose of the TempData attribute in ASP.NET Core?

TempData is used to persist data between requests and is often used to transfer data between actions during a redirect.

23. What is the role of the appsettings.Development.json file?

appsettings.Development.json is a configuration file used to store settings specific to the development environment.

24. How can you enable dependency injection in ASP.NET Core?

Dependency injection is enabled in ASP.NET Core by configuring services in the ConfigureServices method of the Startup class.

25. What is the purpose of the IActionResult interface?

IActionResult is an interface that represents the result of an action method in ASP.NET Core. It allows for different types of responses, such as views, redirects, or JSON data.

26. Explain the concept of View Components in ASP.NET Core?

View Components are similar to partial views but are more powerful, allowing for encapsulation of complex logic and rendering of reusable components in views.

27. How does ASP.NET Core support asynchronous programming?

ASP.NET Core supports asynchronous programming through the extensive use of async and await keywords, allowing non-blocking I/O operations and improving the scalability of web applications.

28. What is the purpose of the ConfigureServices method in Startup.cs?

ConfigureServices is used to configure services such as dependency injection and is called by the runtime when the application starts.

29. Explain the role of the Model-View-Controller (MVC) pattern in ASP.NET Core?

MVC is a design pattern used in ASP.NET Core for separating the application into three components: Model (data and business logic), View (user interface), and Controller (handles user input and updates the model).

30. How can you handle routing in ASP.NET Core?

Routing in ASP.NET Core is handled through the use of the app.UseEndpoints method in the Startup class, where developers can define routes to map URLs to controllers and actions.

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.DependencyInjection;

public class Startup
{
    public void ConfigureServices(IServiceCollection services)
    {
        // Configuration of services (if any)
    }

    public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
    {
        if (env.IsDevelopment())
        {
            app.UseDeveloperExceptionPage();
        }
        else
        {
            app.UseExceptionHandler("/Home/Error");
            app.UseHsts();
        }

        app.UseRouting();

        app.UseEndpoints(endpoints =>
        {
            endpoints.MapGet("/", async context =>
            {
                await context.Response.WriteAsync("Hello, World!");
            });

            endpoints.MapControllerRoute(
                name: "default",
                pattern: "{controller=Home}/{action=Index}/{id?}");
        });
    }
}

ASP.NET Core Interview Questions For Experience

1. Explain the role of the ConfigureServices method in the Startup.cs file?

The ConfigureServices method is used to configure services for dependency injection in ASP.NET Core. It’s called at application startup and is where services like databases, authentication, and other dependencies are registered.

2. How does ASP.NET Core handle configuration management, and what are the various sources of configuration?

ASP.NET Core uses the IConfiguration interface for configuration management. Configuration can come from various sources, including appsettings.json files, environment variables, command-line arguments, and more.

3. Describe the use of the async/await keywords in ASP.NET Core?

Async/await is used for asynchronous programming in ASP.NET Core to improve scalability by allowing non-blocking I/O operations. It is commonly used with tasks to perform operations without blocking the main thread.

4. How can you implement authentication and authorization in ASP.NET Core?

Authentication is implemented using middleware such as Identity, while authorization is handled with attributes like [Authorize]. Policies and roles can also be used for more granular control.

5. What is the purpose of the UseExceptionHandler middleware?

UseExceptionHandler is used to catch unhandled exceptions globally in an ASP.NET Core application, allowing for centralized error handling and logging.

6. Explain the role of the IWebHostEnvironment interface in ASP.NET Core?

IWebHostEnvironment provides information about the hosting environment, allowing developers to adjust behavior based on whether the application is running in development, production, or another environment.

7. How does ASP.NET Core support versioning of APIs?

ASP.NET Core supports API versioning through various methods, including URL-based versioning, header-based versioning, and query parameter-based versioning. This allows for backward compatibility when evolving APIs.

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.DependencyInjection;

public class Startup
{
    public void ConfigureServices(IServiceCollection services)
    {
        services.AddControllers();

        // Configure API versioning
        services.AddApiVersioning(options =>
        {
            options.DefaultApiVersion = new ApiVersion(1, 0);
            options.AssumeDefaultVersionWhenUnspecified = true;
            options.ReportApiVersions = true;
        });
    }

    public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
    {
        if (env.IsDevelopment())
        {
            app.UseDeveloperExceptionPage();
        }
        else
        {
            app.UseExceptionHandler("/Home/Error");
            app.UseHsts();
        }

        app.UseRouting();

        app.UseEndpoints(endpoints =>
        {
            endpoints.MapControllers();
        });
    }
}

8. What is the purpose of the [ApiController] attribute in ASP.NET Core?

The [ApiController] attribute in ASP.NET Core is used to indicate that a controller is an API controller, enabling features such as automatic model validation and binding source parameter inference.

9. Explain the concept of Dependency Injection in ASP.NET Core and how it promotes modular and testable code?

Dependency Injection in ASP.NET Core allows for the injection of dependencies into components, promoting loose coupling. This enhances modularity, testability, and maintainability of the code.

10. How can you handle cross-site request forgery (CSRF) protection in ASP.NET Core?

CSRF protection in ASP.NET Core is implemented by using anti-forgery tokens. Developers can include the [ValidateAntiForgeryToken] attribute on actions or use the antiforgery middleware.

11. Describe the role of Tag Helpers in ASP.NET Core views?

Tag Helpers are a way to simplify the syntax and readability of HTML in Razor views. They enable server-side logic within HTML tags, providing a more natural and maintainable way to work with server-side code.

12. Explain the purpose of the appsettings.Development.json file?

appsettings.Development.json is a configuration file specific to the development environment, allowing developers to override settings for debugging and development purposes.

13. How can you optimize performance in an ASP.NET Core application?

Performance optimization can be achieved through various techniques, including asynchronous programming, caching, using a Content Delivery Network (CDN), and optimizing database queries.

14. What is the role of the IApplicationBuilder in the ASP.NET Core middleware pipeline?

IApplicationBuilder is used to configure the request processing pipeline in ASP.NET Core. Middleware components are added and configured using the IApplicationBuilder instance in the Configure method of the Startup class.

15. Explain the purpose of the [FromBody] attribute in ASP.NET Core controllers?

The [FromBody] attribute is used in ASP.NET Core controllers to indicate that the parameter value should be bound from the request body. It is commonly used when working with complex types in POST or PUT requests.

16. How can you implement logging in ASP.NET Core?

Logging in ASP.NET Core is implemented using the built-in logging framework. Developers can use the ILogger interface and various logging providers like Console, Debug, or third-party providers for more advanced logging features.

17. What is the role of the Reverse Proxy in ASP.NET Core deployments?

A Reverse Proxy is often used in ASP.NET Core deployments to handle tasks like load balancing, SSL termination, and forwarding requests to the appropriate backend server. Popular choices include Nginx and Apache.

18. Explain the concept of Output Caching in ASP.NET Core?

Output Caching in ASP.NET Core involves caching the output of a controller action or an entire page, reducing the need to regenerate the content for subsequent requests and improving performance.

19. How can you implement health checks in an ASP.NET Core application?

Health checks are implemented using the Health Checks middleware in ASP.NET Core. Developers can configure custom health checks to monitor the application’s state and report its status.

20. Explain how ASP.NET Core handles asynchronous streaming of large files?

ASP.NET Core supports asynchronous streaming of large files through the use of the IFormFile interface, allowing developers to read and process file uploads in a non-blocking manner.

21. How can you handle authentication and authorization in a microservices architecture using ASP.NET Core?

In a microservices architecture, authentication and authorization are often implemented using a combination of OAuth 2.0, OpenID Connect, and JSON Web Tokens (JWTs). Services can rely on a centralized identity provider for authentication.

22. How can you implement and configure Swagger/OpenAPI for documenting APIs in ASP.NET Core?

Swagger/OpenAPI can be implemented using the Swashbuckle.AspNetCore library. Developers can configure it in the Startup class to automatically generate API documentation, making it easier for clients to understand and consume APIs.

ASP.NET Core Developers Roles and Responsibilities

The roles and responsibilities of an ASP.NET Core developer may vary based on the specific job description and the organization’s requirements. However, here is a list of common roles and responsibilities that ASP.NET Core developers typically have:

1. Application Development: Develop and maintain web applications using ASP.NET Core, ensuring high performance, responsiveness, and security.Collaborate with cross-functional teams to define, design, and ship new features.Write clean, scalable, and maintainable code.
2. ASP.NET Core Expertise: Demonstrate a strong understanding of the ASP.NET Core framework and its features.Utilize best practices and design patterns in ASP.NET Core development.
3. Database Integration: Design and implement database models using Entity Framework Core or other data access technologies. Optimize database queries for performance and efficiency.
4. Front-End Integration: Collaborate with front-end developers to integrate server-side logic with user interfaces. Ensure seamless communication between the front-end and back-end components.
5. API Development: Design and implement RESTful APIs for communication between different modules or external services.Implement authentication and authorization mechanisms for APIs.
6. Middleware Configuration: Configure middleware components to handle various aspects of the request-response pipeline, such as authentication, logging, and error handling.
7. Dependency Injection: Implement and utilize dependency injection to achieve loose coupling and maintainability in the codebase.
8. Testing: Write unit tests and perform integration testing to ensure the reliability and correctness of the code. Implement test-driven development (TDD) practices where applicable.
9. Security Implementation: Implement security best practices, including data encryption, secure communication (HTTPS), and protection against common web vulnerabilities (e.g., Cross-Site Scripting, Cross-Site Request Forgery).
10. Performance Optimization: Identify and optimize performance bottlenecks in the application, both on the server-side and database.
11. Version Control: Use version control systems (e.g., Git) effectively to manage source code and collaborate with other developers.
12. Continuous Integration/Continuous Deployment (CI/CD): Set up and maintain CI/CD pipelines to automate the build, test, and deployment processes.
13. Documentation: Create and maintain technical documentation, including code documentation, API documentation, and system architecture documentation.
14. Troubleshooting and Debugging: Debug and troubleshoot issues reported by users or identified through monitoring tools. Implement logging and monitoring mechanisms to aid in debugging and issue resolution.
15. Code Reviews: Participate in code reviews to ensure code quality, adherence to coding standards, and knowledge sharing within the development team.
16. Performance Monitoring: Implement monitoring solutions to track the performance and health of the application. Respond to performance-related issues promptly.
17. Stay Updated: Stay informed about the latest advancements in ASP.NET Core, web development, and related technologies. Attend conferences, webinars, and training sessions to continuously enhance skills and knowledge.
18. Collaboration: Collaborate with other team members, including UX/UI designers, product owners, and QA engineers, to deliver high-quality software.
19. Agile Development: Work within an Agile development environment, participate in sprint planning, and contribute to iterative development cycles.
20. Adaptability: Adapt to evolving technologies, methodologies, and project requirements.

These responsibilities outline the diverse skill set and tasks typically associated with an ASP.NET Core developer role. Depending on the organization and project specifics, some roles may be more emphasized than others.

Frequently Asked Questions