ASP.NET Core MVC Experienced Interview Questions and Answers

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ASP.NET Core MVC Experienced Interview Questions and Answers

In this article, I will discuss the most frequently asked Top 50 ASP.NET Core MVC Experienced Interview Questions and Answers. Please read our previous article discussing the Top 50 ASP.NET Core MVC Intermediate Interview Questions and Answers. When preparing for an interview focused on ASP.NET Core MVC, it’s crucial to cover a wide range of topics, from basics to advanced features. Here’s a comprehensive list of ASP.NET Core MVC Experienced Interview Questions and Answers.

Explain the startup process of an ASP.NET Core application.

The startup process of an ASP.NET Core application begins with the Program.cs file, which sets up the host. The host is responsible for app startup and lifetime management. The next significant step is in the Program.cs file, where you configure services needed by your app and set up your app’s request processing pipeline with middleware in the Main method.

How does the ASP.NET Core request pipeline work?

The request pipeline in ASP.NET Core is composed of a series of middleware components. Each component performs operations on an HttpContext and either calls the next middleware in the sequence or terminates the request. The pipeline is configured in the Main method of the Program.cs file. Middleware can handle tasks like routing, authentication, and serving static files.

Describe the purpose and use of the Startup.cs file in ASP.NET Core.

The Startup.cs file is used to configure services and the request processing pipeline. In the ConfigureServices method, you add services to the DI container. The Configure method is where you define the middleware that handles requests. This setup allows for configuring how the app responds to HTTP requests and integrating essential services like Entity Framework Core, MVC, Identity, etc.

What are the benefits of using ASP.NET Core over ASP.NET?

ASP.NET Core offers several advantages over ASP.NET, including:

• Cross-platform support (Windows, Linux, macOS).
• A lightweight, high-performance, and modular HTTP request pipeline.
• Built-in dependency injection.
• A unified story for building web UI and APIs.
• Support for hosting in Docker containers.
• Improved support for asynchronous programming.

What is the difference between ActionResult and IActionResult in MVC controllers?

ActionResult is an abstract class from which many result types inherit (e.g., ViewResult, FileResult). IActionResult is an interface that all action results implement, providing more flexibility in returning different types of responses from controller actions. Using IActionResult allows for returning various types of action results, enabling more dynamic responses to HTTP requests.

How can you achieve dependency injection in ASP.NET Core controllers?

Dependency injection in ASP.NET Core is achieved primarily through constructor injection. You define the dependencies in the constructor of a controller, and the ASP.NET Core framework’s built-in dependency injection system provides the required services at runtime. Services are registered in the Main method of the Program.cs file.

Explain how to use attribute routing in ASP.NET Core.

Attribute routing is enabled by decorating controllers and actions with attributes that define routes. The [Route] attribute can be applied to a controller or an action to specify the URL pattern it should handle. This allows for more granular and expressive routing compared to conventional routing and supports defining routes directly on the actions and controllers.

Describe the Razor syntax and its benefits in MVC views.

Razor is a markup syntax for embedding server-based code into webpages. The Razor syntax is compact, expressive, and clean, making it easy to mix server code with HTML. Benefits include the ability to use C# in views, IntelliSense support in Visual Studio, and the ability to create reusable, dynamic web UI components.

How do you implement layouts, view starts, and view imports in Razor?

Layouts are used to define a common site template (e.g., header, footer). You specify a layout in a Razor view using @Layout.

• ViewStart files (_ViewStart.cshtml) contain code that is executed for every view. It’s often used to set the layout.
• ViewImports (_ViewImports.cshtml) allows you to import namespaces and add tag helpers globally to views, so you don’t need to do it in every view.

Explain the role of ViewComponents and when to use them over partial views.

ViewComponents are similar to partial views, but they’re more powerful, allowing for the encapsulation of both logic and display. They can execute code to generate their model before rendering. Use ViewComponents when you need to perform complex logic or data fetching before rendering a part of a page, which goes beyond the capabilities of partial views.

What is the difference between Entity Framework Core and Entity Framework 6?

Entity Framework Core is a lightweight, extensible, and cross-platform version of Entity Framework, the .NET ORM for data access. EF Core works with SQL Server, SQLite, Azure Cosmos DB, and more. EF6 is the previous version, designed primarily for use with .NET Framework applications. EF Core introduces new features like shadow properties, global query filters, and better support for asynchronous operations, alongside performance improvements and cross-platform support.

How do you perform model validation in ASP.NET Core MVC?

In ASP.NET Core MVC, model validation is performed using data annotations and by implementing the IValidatableObject interface on the model. Data annotations are attributes that you can apply to model properties, such as [Required], [StringLength], and [Range], to specify validation rules. The framework automatically checks these annotations when a form is submitted and populates the ModelState with any validation errors. You can check ModelState.IsValid in your action methods to determine if the model passed validation. Custom validation logic can also be added by implementing the Validate method of the IValidatableObject interface.

Describe the approach to handle database migrations in ASP.NET Core.

Database migrations in ASP.NET Core are typically managed with Entity Framework Core (EF Core). Migrations allow you to evolve your database schema over time as your application evolves without losing data. To handle migrations, you use commands like Add-Migration to scaffold a migration script for pending schema changes and Update-Database to apply the migration to the database. Migrations include up and down methods, allowing you to apply or revert changes. EF Core tracks applied migrations using a special history table in your database.

What is middleware in the context of ASP.NET Core applications?

Middleware in ASP.NET Core is software that’s assembled into an application pipeline to handle requests and responses. Each component chooses whether to pass the request to the next component in the pipeline and can perform certain actions before and after the next component. Middleware is used for authentication, error handling, static file serving, and more. They are configured in the Configure method of the Startup class using methods like Use….

Explain how to create and register custom middleware.

To create custom middleware in ASP.NET Core, define a class with an Invoke or InvokeAsync method that takes HttpContext as a parameter. This method should perform the middleware’s task and optionally call next to pass control to the next middleware in the pipeline. To register the middleware, add it to the application’s request pipeline using the UseMiddleware<T> extension method in the Main method of the Program class.

Describe the built-in dependency injection container in ASP.NET Core.

ASP.NET Core includes a built-in dependency injection (DI) container that supports constructor injection by default. It allows you to register application services with various lifetimes (singleton, scoped, transient) and resolve them where needed. The DI container promotes loose coupling and makes your application more modular and testable. Services are typically registered in the Main method of the Program class.

What are the different service lifetimes available in ASP.NET Core, and when would you use each?

• Singleton: Only one instance is created for the application’s lifetime. Use for services that are stateless or thread-safe.
• Scoped: A new instance is created for each request. Use for services that are specific to a request, such as database contexts.
• Transient: A new instance is created every time a service is requested. Use for lightweight, stateless services.

How does ASP.NET Core implement authentication and authorization?

ASP.NET Core implements authentication and authorization through middleware. Authentication middleware authenticates a user, and authorization middleware authorizes a user to access resources. ASP.NET Core supports various authentication schemes (e.g., cookie-based, JWT, OAuth) and allows for custom schemes. Authorization can be role-based, policy-based, or a custom implementation configured via attributes or services.

What are some ways to secure an ASP.NET Core MVC application against common vulnerabilities?

To secure an ASP.NET Core MVC application, you should:

• Use HTTPS to protect data in transit.
• Implement proper authentication and authorization.
• Use Data Protection APIs for secure data handling.
• Validate input to prevent SQL injection and XSS attacks.
• Configure CORS policies appropriately.
• Use anti-forgery tokens to prevent CSRF attacks.

Explain Cross-Site Request Forgery (CSRF) and how to prevent it in ASP.NET Core.

CSRF is an attack that tricks the user into submitting a malicious request. ASP.NET Core mitigates CSRF attacks by using anti-forgery tokens. An anti-forgery token is generated and sent to the client; the client must include this token in subsequent potentially unsafe requests (e.g., POST). ASP.NET Core validates the token to ensure the request is not a CSRF attack. This is typically implemented using the [ValidateAntiForgeryToken] attribute on actions and the @Html.AntiForgeryToken() helper in forms.

What are some techniques to optimize the performance of ASP.NET Core applications?

Performance optimization techniques include:

• Minimizing middleware components in the request pipeline.
• Using response caching and in-memory caching.
• Optimizing data access (e.g., using asynchronous methods, batching queries).
• Minimizing the use of synchronous operations.
• Implementing efficient logging.
• Using the latest .NET Core and ASP.NET Core versions for performance improvements.

How do you implement caching in ASP.NET Core?

In ASP.NET Core, caching can be implemented in several ways:

• In-memory caching: Using the IMemoryCache interface to store objects in memory.
• Distributed caching: Using a distributed cache (e.g., Redis, SQL Server) that can be shared across multiple servers or instances.
• Response caching: Using response caching middleware to cache HTTP responses for subsequent requests.

Each caching strategy has its use cases, depending on the scalability needs and the nature of the data being cached.

Use of asynchronous programming in ASP.NET Core to enhance performance:

Asynchronous programming in ASP.NET Core allows non-blocking operations. It enables the webserver to handle more requests by not waiting for long-running tasks (like I/O operations) to complete. This is achieved using async and await keywords in C#. Asynchronous methods improve scalability and responsiveness, particularly in web applications that interact with databases or external services.

Unit testing an ASP.NET Core MVC controller:

To unit test an ASP.NET Core MVC controller, you can use a testing framework like xUnit, NUnit, or MSTest, along with a mocking library such as Moq. The idea is to instantiate the controller with mock dependencies passed into its constructor and then call the action methods on the controller object. Assertions are made on the result to verify the controller behaves as expected, focusing on the logic within action methods without worrying about infrastructure concerns like databases, file systems, or network calls.

Role of integration testing in ASP.NET Core and how it is performed:

Integration testing ensures that different parts of the application work together as expected. In ASP.NET Core, this involves testing controllers, views, databases, and other components as a whole. It can be performed using the Microsoft.AspNetCore.Mvc.Testing package, which allows running an in-memory test server with a real HTTP stack. Integration tests typically make real HTTP requests to the application and assert the responses to ensure the application behaves correctly when all pieces are integrated.

Use of SignalR in ASP.NET Core:

SignalR is a library for ASP.NET Core that enables real-time web functionality. It allows server-side code to send asynchronous notifications to client-side web applications. SignalR is used for adding chat features, real-time updates, and interactive features to web applications. It uses WebSockets under the hood when available and falls back to other compatible techniques for real-time communication when necessary.

Areas in ASP.NET Core MVC and their benefits:

Areas are a feature in ASP.NET Core MVC that helps organize a large project into smaller functional groupings. Each area can contain its own set of controllers, views, and models. This organization makes it easier to manage and scale large applications by allowing teams to work on distinct features in isolation, improving the maintainability and structure of the application.

Implementing API versioning in ASP.NET Core:

API versioning in ASP.NET Core can be achieved through query string parameters, URL paths, or HTTP headers. The Microsoft.AspNetCore.Mvc.Versioning package offers easy-to-use services and attributes that help manage versioned APIs. By specifying versions on controllers or actions, you can ensure that APIs are backward compatible and clients can choose which version of the API they want to call.

Internationalization and localization in ASP.NET Core:

ASP.NET Core supports internationalization (creating applications that support multiple cultures) and localization (adapting an application for a specific culture/locale). This involves using Resource Files (.resx) to store localized strings and configuring services in Program.cs to use localization middleware. The framework provides mechanisms to detect the user’s culture and apply the appropriate resources, allowing developers to create globally accessible applications.

Deploying an ASP.NET Core application to a Linux server:

Deployment to a Linux server involves publishing the ASP.NET Core application, transferring the published application to the server, and hosting it using a reverse proxy server like Nginx or Apache. The application can run on Linux using the Kestrel web server and be managed as a systemd service for start-up and logging. Additionally, setting up an SSL certificate using Let’s Encrypt might be necessary for secure HTTPS connections.

Managing app settings and configurations for different environments in ASP.NET Core:

ASP.NET Core uses an environment-specific appsettings.json file (e.g., appsettings.Development.json, appsettings.Production.json) to override settings in the appsettings.json file based on the environment. The IConfiguration interface is used to access these settings in the code. Environment variables can further override these settings, providing flexibility for different deployment environments without changing the code.

Role of the appsettings.json file in ASP.NET Core:

The appsettings.json file is the default configuration file in ASP.NET Core applications. It stores configuration settings such as connection strings, logging levels, and application-specific settings. These settings can be read at runtime using the IConfiguration service.

Managing user sessions in ASP.NET Core MVC:

User sessions in ASP.NET Core MVC are managed through the session middleware, which stores session data on the server. Sessions are configured in Program.cs and can store data per user across requests. Session data can be used for storing user-specific data like IDs, shopping cart items, or user preferences during a browser session.

Concept of Tag Helpers in ASP.NET Core and its advantages:

Tag Helpers enable server-side code to participate in creating and rendering HTML elements in Razor files. They provide a way to enhance and extend HTML tags with server-side behaviors. Tag Helpers make Razor views more readable and maintainable by adding server-side processing power without the cumbersome syntax of traditional Razor or HTML Helpers. They are used for form submissions, linking to resources, and dynamically generating HTML content.

ASP.NET Core support for real-time web functionality:

ASP.NET Core supports real-time web functionality primarily through SignalR. It allows for the development of web applications that require high-frequency updates from the server, such as chat applications, live notifications, and real-time dashboards.

Options pattern in ASP.NET Core for configuration:

The options pattern uses classes to represent groups of related settings. By injecting these classes using dependency injection, applications can access configured settings. This pattern is implemented through the IOptions<T> interface, providing a strong-typed way to access settings in the appsettings.json file or other configuration sources, making the configuration system more robust and easier to maintain.

How do you secure sensitive data in ASP.NET Core applications?

Securing sensitive data in ASP.NET Core applications involves several practices:

• Data Encryption: Use encryption to protect data at rest and in transit. ASP.NET Core supports encryption mechanisms like AES for sensitive data and TLS for data in transit.
• Secrets Management: Avoid storing sensitive data in your code or configuration files. Use secret managers like Azure Key Vault or the Secret Manager tool during development.
• Data Protection API: Utilize the ASP.NET Core Data Protection API for encrypting and securing data, especially for cookies and session information.

What are some best practices for error handling and logging in ASP.NET Core?

• Global Exception Handling: Use middleware to handle global exceptions, catch unhandled exceptions, and log them.
• Use Logging Frameworks: Implement logging frameworks like Serilog or NLog to log errors and application flow for diagnostics.
• Structured Logging: Adopt structured logging to log complex data types in a structured format, making it easier to query logs.
• Error Handling Pages: Configure custom error pages for different types of exceptions to provide a better user experience.

How can the Repository and Unit of Work patterns be applied in ASP.NET Core applications?

• Repository Pattern: Implement the repository pattern to abstract the data layer, making your application more maintainable and testable. Each repository handles the data operations for a single entity type.
• Unit of Work: Use the Unit of Work pattern to maintain a list of transactions and coordinate the writing out of changes and the resolution of concurrency problems. It often works alongside the repository pattern to ensure that multiple repositories can commit changes atomically.

Describe the CQRS pattern and its applicability in ASP.NET Core.

CQRS (Command Query Responsibility Segregation) is a design pattern that separates the read and update operations for a data store. Implementing CQRS in ASP.NET Core can improve performance, scalability, and security, as it allows you to scale read and write operations independently and optimize each path according to its demands.

How do you secure Web APIs in ASP.NET Core?

Securing Web APIs in ASP.NET Core typically involves:

• Authentication: Use ASP.NET Core Identity for user authentication or external providers via OAuth2/OpenID Connect.
• Authorization: Implement authorization policies to control access to resources based on user roles or claims.
• API Keys: Use API keys for simpler scenarios where full OAuth flows are not required.
• HTTPS: Enforce HTTPS to protect data in transit.

Discuss strategies for developing and deploying microservices with ASP.NET Core.

• Domain-Driven Design (DDD): Adopt DDD to define clear microservice boundaries based on business domains.
• Containerization: Use Docker containers to package and deploy microservices independently.
• API Gateway: Implement an API Gateway to route requests, aggregate responses, and enforce common concerns like SSL termination and authentication.
• Health Checks: Utilize health checks to monitor the status of microservices.

How do you set up a CI/CD pipeline for an ASP.NET Core application?

Setting up a CI/CD pipeline involves:

• Source Control: Use Git for source control.
• Build Server: Use a build server like Azure DevOps, Jenkins, or GitHub Actions to automate builds.
• Automated Testing: Incorporate unit tests and integration tests in your CI pipeline.
• Deployment Automation: Use deployment tools or scripts to automate the deployment to different environments (development, staging, production).

What are the benefits of using containerization with ASP.NET Core applications?

Containerization offers:

• Portability: Containers encapsulate the application and its dependencies, making it easy to run across different environments.
• Isolation: Each container runs in isolation, improving security and reducing conflicts between applications.
• Scalability: Containers can be easily scaled up or down to handle load changes.
• Continuous Deployment: Containers fit well into CI/CD pipelines, enabling rapid deployment.

How can background tasks be implemented in ASP.NET Core?

Background tasks in ASP.NET Core can be implemented using hosted services or background worker classes. These allow you to run background operations, like processing tasks in a queue, without blocking the main application thread.

Explain how to use environment variables to configure ASP.NET Core applications in different environments.

ASP.NET Core supports configuration through various sources, including environment variables. By using environment variables, you can override settings in appsettings.json based on the deployment environment, such as development, staging, or production, allowing for flexible and secure configuration.

Discuss the role and configuration of the Kestrel web server in ASP.NET Core.

Kestrel is a cross-platform web server for ASP.NET Core. It can run as a standalone server or behind a reverse proxy like IIS or Nginx. Configuring Kestrel involves setting up HTTPS, configuring endpoints, and setting limits on requests and connections for security and performance.

How do you customize the built-in Identity system in ASP.NET Core for user authentication and authorization?

Customizing ASP.NET Core Identity involves:

• Extending Identity Models: Extend user and role models to include additional properties.
• Custom Stores: Implement custom user and role stores if you need to store identity data in a non-standard way.
• Custom Password Policies: Configure password strength, lockout settings, and user validation rules.
• Claims-Based Authorization: Use claims to store additional user metadata for fine-grained access control.

In this article, I provided the list of Frequently Asked Top 50 ASP.NET Core MVC Experienced Interview Questions and Answers. I hope you enjoy this article on ASP.NET Core MVC Experienced Interview Questions and Answers.

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