ASP.NET Core MVC Basic Interview Questions and Answers

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ASP.NET Core MVC Basic Interview Questions and Answers

In this article, I will discuss the most frequently asked Top 50 ASP.NET Core MVC Basic Interview Questions and Answers. Please read our previous article discussing the Top 50 ASP.NET Core Experienced 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 Basic Interview Questions and Answers.

What is ASP.NET Core MVC, and how does it differ from ASP.NET MVC?

ASP.NET Core MVC is a modern, cloud-optimized framework for building web applications and APIs based on the Model-View-Controller (MVC) design pattern. It is a part of ASP.NET Core, which is a complete rewrite of the classic ASP.NET 4.x, with architectural changes to make it leaner, more modular, and cross-platform.

Differences from ASP.NET MVC:

• Cross-Platform: ASP.NET Core MVC can run on Windows, Linux, and macOS, whereas ASP.NET MVC is limited to Windows.
• Performance: ASP.NET Core is designed for high performance, benefiting from the Kestrel web server and various optimizations.
• Modularity: ASP.NET Core introduces a modular HTTP request pipeline, allowing developers to add only the components they need, enhancing performance and simplification.
• Configuration: Configuration is more flexible and cloud-optimized in ASP.NET Core, supporting JSON, XML, and other formats, rather than being limited to Web.config.
• Dependency Injection: Built-in support for dependency injection in ASP.NET Core MVC, whereas ASP.NET MVC requires third-party libraries for this.

Explain the MVC architecture.

The MVC architecture divides an application into three interconnected components, each with specific responsibilities:

• Model: Represents the data and the business logic of the application. It is responsible for accessing and storing data and defining the business rules.
• View: Responsible for displaying the user interface and presenting data to the user. It displays the model data and sends user actions (e.g., button clicks) to the controller.
• Controller: Acts as an intermediary between the Model and the View. It processes incoming requests, performs operations on the model, and selects a view to render the UI.

This separation helps manage complexity, enabling more efficient development and testing of applications.

What are the advantages of using ASP.NET Core MVC?

• Cross-Platform: Develop and deploy on Windows, Linux, or macOS.
• High Performance: Optimized for speed and scalable applications.
• Modularity: Only include necessary components, reducing overhead.
• Support for Modern Web Development: Built-in support for modern UI frameworks and Web APIs.
• Robust Ecosystem: Access to a wide range of libraries and tools.
• Built-in Dependency Injection: Simplifies application development and testing.
• Security: Enhanced security features and best practices to protect applications.

Describe the role of a Controller in an MVC application.

In an MVC application, a Controller handles user interactions, works with the Model to perform operations, and selects a View to render that displays the UI. The controller responds to user input, interacts with the model to retrieve data or execute business logic, and then passes that data to the view for presentation.

How does routing work in ASP.NET Core MVC?

Routing in ASP.NET Core MVC maps incoming requests to controller actions. It uses route templates defined in the startup configuration to determine the controller and action method to execute based on the URL. Routes can be configured using attribute routing on controllers and actions or by defining routes in the Program.cs file. This allows developers to design custom URL patterns that are readable and meaningful.

What is Dependency Injection, and how is it implemented in ASP.NET Core?

Dependency Injection (DI) is a design pattern that allows for the creation of loosely coupled components. In ASP.NET Core, DI is built into the framework, allowing services to be injected into classes rather than being tightly coupled. This is implemented using a container that manages the lifetimes of objects and their dependencies. You define services in the Program.cs file and the framework takes care of creating and injecting instances where needed.

Explain the concept of Middleware in the context of ASP.NET Core.

Middleware in ASP.NET Core are components that are assembled into an application pipeline to handle requests and responses. Each component performs operations before and/or after the next component. Middleware can perform a wide range of tasks, such as authentication, routing, logging, and serving static files. You configure the middleware pipeline in the Program.cs file.

What are Action Methods in MVC?

Action methods in MVC are methods within a controller that respond to HTTP requests. They are responsible for executing the logic needed to process the request and generate a response, which could be a view, a file, a redirect, or a JSON response for APIs. The framework maps incoming requests to action methods based on the route data and HTTP method.

How do you pass data from a Controller to a View?

In ASP.NET MVC, data can be passed from a Controller to a View using several methods, including ViewData, ViewBag, and TempData, as well as strongly typed views using model binding. Here’s a brief overview of each:

• ViewData is a dictionary object that allows data to be passed from the controller to the view. It requires typecasting for complex data types and checks for null values to avoid runtime errors.
• ViewBag uses dynamic properties to hold the data. It’s a wrapper over ViewData, providing a more dynamic feature but sharing the same limitations, such as the need for typecasting and null checks.
• TempData is used to pass data from the current request to the next request. It’s based on session state and is helpful for redirect scenarios.

What is Razor Syntax?

Razor is a markup syntax for embedding server-based code into webpages. The Razor syntax allows for quick and more natural coding in ASP.NET web pages (.cshtml files) with C# or VB.Net. It combines markup with C# or VB directly in the same file, with a minimalistic syntax that reduces the amount of code required for common tasks. Razor pages are processed on the server before they’re sent to the browser.

Describe ViewData, ViewBag, and TempData.

• ViewData: A dictionary object that is derived from the ViewDataDictionary class. It’s used to pass data from a controller to a view. It requires casting for complex types and checking for null values, as it can hold data of any type.
• ViewBag: A dynamic property that provides a dynamic view over the ViewData. Since it’s dynamic, it doesn’t require typecasting, but you still need to check for null values. It’s a more flexible and cleaner way to pass data to the view, though it has the same limitations regarding the lifespan of data as ViewData.
• TempData: Used to pass data from one action method to another within the same or a different controller. TempData is also stored in ViewDataDictionary, but it’s intended for temporary data that needs to be retained until it’s read. TempData uses session variables for storage and is useful for redirect scenarios, where data needs to be preserved between requests.

What are View Components?

View Components in ASP.NET MVC are similar to partial views, but they’re much more powerful. They allow for the creation of reusable components (or widgets) that can encapsulate rendering logic and data access separately from the main views and controllers. A view component includes two main parts: the class (usually derived from ViewComponent) that contains the logic to generate the data needed for the view and the view itself, which renders the UI. View components are invoked within views using the Component.InvokeAsync method and can be used to create dynamic elements in web applications, such as a shopping cart, recent articles list, or a login panel, without tightly coupling the view to a specific model or controller logic.

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

Form validation in ASP.NET Core MVC can be achieved using Data Annotations and the built-in validation support in the framework. You can decorate model properties with validation attributes like [Required], [StringLength], [Range], etc. The framework automatically validates incoming data against these annotations when the model is passed to an action method, and it populates ModelState with any validation errors. You can check ModelState.IsValid in your controller actions to determine if the data is valid.

Explain the use of the [Authorize] attribute.

The [Authorize] attribute is used to enforce authorization on MVC controllers and actions. It ensures that only authenticated users can access certain parts of your application. You can also use it with roles or policies to authorize based on more specific criteria, like user roles or permissions.

What is the difference between AddSingleton, AddScoped, and AddTransient services?

• AddSingleton: Registers a service as a singleton, which means a single instance of the service is created and shared throughout the application’s lifetime.
• AddScoped: Registers a service with a scope lifetime, which means a new instance is created for each request but shared within a single request.
• AddTransient: Registers a service with a transient lifetime, meaning a new instance is created every time the service is requested.

How does ASP.NET Core handle exceptions?

ASP.NET Core handles exceptions using middleware, such as the built-in Developer Exception Page for development environments and the Exception Handler Middleware for production. You can also create custom exception handling middleware or use filters like the ExceptionFilterAttribute for more granular control over exception handling within MVC actions.

What are Filters in ASP.NET Core MVC? Give examples.

Filters in ASP.NET Core MVC allow you to run code before or after specific stages in the request processing pipeline, such as authorization, action execution, and result processing. Examples include:

• Authorization filters ([Authorize]): Check if a user is authorized to perform an action.
• Action filters (OnActionExecuting, OnActionExecuted): Execute code before or after an action method runs.
• Exception filters ([ExceptionFilter]): Handle exceptions thrown by action methods.

What is the purpose of the appsettings.json file?

The appsettings.json file is used for configuration in ASP.NET Core applications. It stores configuration data, such as connection strings, logging settings, and application-specific settings, in a JSON format. This file can be environment-specific, allowing for different settings in development, testing, and production environments.

How do you secure an ASP.NET Core MVC application?

Securing an ASP.NET Core MVC application involves multiple strategies, including:

• Using the [Authorize] attribute to protect resources.
• Implementing secure authentication mechanisms (e.g., ASP.NET Core Identity for login functionality).
• Applying HTTPS to ensure encrypted data transmission.
• Preventing Cross-Site Scripting (XSS) and Cross-Site Request Forgery (CSRF) attacks.
• Managing user permissions and roles effectively.

Explain CORS. How do you enable it in ASP.NET Core?

CORS (Cross-Origin Resource Sharing) is a security feature that allows or restricts web applications from making requests to domains other than their own. In ASP.NET Core, you can enable CORS by configuring the CORS middleware in the Program.cs file. You use the AddCors method to define a policy and UseCors to apply it, specifying which origins, headers, and methods are allowed.

What is the difference between a synchronous and asynchronous action method?

A synchronous action method blocks the thread it runs on until it completes its execution, which can lead to poor performance under high load. An asynchronous action method, on the other hand, uses async and await keywords to free up the thread for other tasks while awaiting asynchronous operations, leading to better scalability and responsiveness.

How do you manage sessions in ASP.NET Core?

Sessions in ASP.NET Core are managed using the session middleware, which stores session data on the server and identifies sessions using a cookie sent to the browser. You can configure session behavior in the Startup.cs file, and then use HttpContext.Session to set or get session data within your controllers.

Explain how to use Areas in ASP.NET Core MVC to organize a large application.

Areas provide a way to partition a large ASP.NET Core MVC application into smaller functional groups, each with its own set of controllers, views, and models. You define areas by creating a folder structure within your project and decorating controllers with the [Area(“AreaName”)] attribute. This helps organize and manage large applications by grouping related functionalities.

What is Entity Framework Core?

Entity Framework Core (EF Core) is an open-source, lightweight, extensible version of Entity Framework, a popular Object-Relational Mapping (ORM) framework for .NET. EF Core enables .NET developers to work with a database using .NET objects, eliminating the need for most of the data-access code that developers usually need to write. It supports LINQ queries, change tracking, updates, and schema migrations.

What is the use of Program.cs file?

The Program.cs file serves as the entry point for an ASP.NET Core application. It contains the Main method, which kicks off the execution of the application. The primary responsibilities of the Program.cs file have evolved with different versions of ASP.NET Core, but generally, it’s where the application’s host is configured and built. In ASP.NET Core applications, the host is responsible for app startup and lifetime management.

Key responsibilities and features of the Program.cs file includes:

• Building the Web Host: It specifies how the application should start and configure services needed by the app. This includes setting up the web server (e.g., Kestrel), loading app configurations from various sources (like appsettings.json, environment variables), and configuring logging.
• Configuring Services: It allows you to add services to the dependency injection (DI) container through the IServiceCollection. This includes framework services (like MVC, Razor Pages), your own application services, and third-party services.
• Middleware Configuration: Although the actual configuration of middleware happens in the Startup.cs file’s Configure method, the Program.cs file sets the stage for this configuration by establishing the application’s host which the Startup.cs utilizes.
• Configuring Application Settings: It’s responsible for configuring app settings and environments, which can influence how the application behaves under different conditions (development, staging, production).
• Running the Application: Finally, it includes the code to run the web application, which listens for incoming HTTP requests.

Describe how to implement API Versioning in ASP.NET Core.

API versioning in ASP.NET Core can be implemented using Microsoft.AspNetCore.Mvc.Versioning package. After installing this package, you can configure versioning in the Startup.cs file by adding services for API versioning in the ConfigureServices method. You can specify the versioning scheme (e.g., query string, URL path, header, or media type) and default version. Controllers or actions can then be decorated with version attributes (e.g., [ApiVersion(“1.0”)]).

How do you enable logging in ASP.NET Core?

Logging in ASP.NET Core is configured in the Program.cs file using the ILoggingBuilder interface. You can specify different logging providers (e.g., Console, Debug, EventSource, EventLog) and set the minimum logging levels. The logging framework is built-in and supports a default set of logging providers, but you can also add third-party providers.

What is the significance of the wwwroot folder in ASP.NET Core?

The wwwroot folder in ASP.NET Core is the web root folder that contains static assets such as HTML, CSS, JavaScript, and image files. It is the root directory for public static content served by the application. Files in this folder can be served directly to clients unless specifically restricted by the application configuration.

Explain the differences between the SQL Server and SQLite extensions for Entity Framework Core.

The SQL Server and SQLite extensions for Entity Framework Core provide the necessary functionality to interact with their respective databases. The main differences lie in their intended use cases (SQL Server for full-scale production databases and SQLite for lightweight, local, and embedded databases), syntax differences for certain SQL operations, and support for different features and data types specific to each database engine.

What is a Partial View in ASP.NET Core MVC?

A Partial View in ASP.NET Core MVC is a reusable view component that can be embedded within other views. It is used to break down large views into smaller, manageable components. Partial views are rendered using the Html.Partial or Html.RenderPartial methods and can be used to display reusable content or widgets across multiple views.

How do you handle file uploads in ASP.NET Core MVC?

File uploads in ASP.NET Core MVC can be handled using the IFormFile interface in action methods. The HTML form must include enctype=”multipart/form-data” attribute. Within the action method, you can access uploaded files through parameters of type IFormFile and use methods like CopyTo or CopyToAsync to save the files to the server.

What is SignalR, and how is it used in ASP.NET Core?

SignalR is a library for ASP.NET Core that enables real-time web functionality, allowing server-side code to push content to clients instantly. It is used for developing applications that require high-frequency updates from the server, such as chat applications, real-time dashboards, or live notifications. SignalR abstracts various transport mechanisms and provides a simple API for connection management, broadcasting messages, and handling events.

How do you implement WebSockets in ASP.NET Core?

WebSockets in ASP.NET Core are implemented by enabling the WebSocket protocol in the Program.cs file within the Configure method using the app.UseWebSockets extension method. You then handle WebSocket requests by accepting a WebSocket connection and performing read/write operations on the WebSocket instance.

What are Tag Helpers in ASP.NET Core MVC?

Tag Helpers in ASP.NET Core MVC are server-side code that participates in creating and rendering HTML elements in Razor views. They enable a clean and server-side way to generate and configure HTML elements, enhancing the development workflow by providing a more HTML-like experience for Razor markup. Tag Helpers are used to create forms and links, load resources, and more.

How do you customize the built-in Identity framework?

The built-in Identity framework in ASP.NET Core can be customized by extending identity models (e.g., ApplicationUser), implementing custom validation, and configuring Identity options (password strength, lockout settings, etc.) in the Startup.cs file. You can also override default behaviors by providing custom implementations for interfaces provided by the Identity framework.

What is the role of the IApplicationBuilder interface?

The IApplicationBuilder interface is used in the Configure method of the Startup.cs file to configure the HTTP request pipeline of an ASP.NET Core application. Middleware components are added to the application pipeline using extension methods on IApplicationBuilder, defining how the application responds to HTTP requests. The order of middleware registration is significant as it dictates the order of execution for request processing and response generation.

How do you perform unit testing in an ASP.NET Core MVC application?

Unit testing in ASP.NET Core MVC applications involves testing individual components or units of the application in isolation, typically using a testing framework like xUnit, NUnit, or MSTest. You create test methods to verify the behavior of your application’s methods, focusing on logic contained within controllers, services, and other parts of the application. Using dependency injection, you can mock dependencies to these units, such as database contexts or custom services, to ensure tests run in isolation without requiring external resources.

What is the difference between an IActionResult and a ViewResult?

IActionResult is an interface that represents the result of an action method in ASP.NET Core MVC. It’s a way to abstract the type of response from the action method. ViewResult is a concrete implementation of IActionResult that represents a view being returned to the user. While IActionResult allows for flexibility in the type of result (views, file downloads, redirects, etc.), ViewResult is specifically used when the response is a view.

How do you implement custom error pages in ASP.NET Core MVC?

Custom error pages can be implemented using the UseStatusCodePagesWithReExecute middleware in the Configure method of Startup.cs. This middleware intercepts responses with specific status codes (like 404 or 500) and re-executes the request pipeline using a specified path to a controller action or page that renders the custom error view.

Explain the role of the IHostingEnvironment interface.

The IHostingEnvironment interface, now replaced by IWebHostEnvironment in ASP.NET Core 3.0, and later provides information about the web hosting environment an application is running in. It includes properties for determining the environment name (Development, Staging, Production, etc.), checking if the application is in a development environment, and accessing the content root and webroot file paths. It’s useful for configuring services and behaviors differently based on the environment.

What is Dependency Injection’s role in configuring logging?

Dependency Injection (DI) in ASP.NET Core is used to inject instances of logging services into classes, such as controllers or custom services, throughout an application. By configuring logging providers (e.g., console, debug, event source) in the Main method of the Program.cs, you make these services available for DI. This allows for flexible and decoupled logging configurations that can be easily modified or extended.

How do you use environment variables in ASP.NET Core?

Environment variables in ASP.NET Core are used to store configuration settings that may vary between different environments (development, staging, production). You can access these variables using the IConfiguration interface, which is typically injected into classes where configuration settings are needed. Environment variables can be set in various ways, including in the operating system, through the launchSettings.json file for development, or using the appsettings.{Environment}.json configuration files.

What is the Kestrel web server, and how does it differ from IIS?

Kestrel is a cross-platform web server for ASP.NET Core applications. It’s lightweight and can be run directly from the command line or as a service. Unlike IIS, which is a Windows-only web server and operates as a reverse proxy, Kestrel can run as an edge server exposed to the internet or behind a reverse proxy like IIS, Nginx, or Apache. Kestrel is designed to be fast and supports full ASP.NET Core feature set.

How do you implement globalization and localization in ASP.NET Core MVC?

Globalization and localization involve designing applications with support for multiple cultures and languages. In ASP.NET Core MVC, this is achieved by using resource files for different languages and cultures, configuring services in Startup.cs to support requested cultures, and using IStringLocalizer<T> or IViewLocalizer to retrieve localized strings in controllers and views, respectively.

What are static files in ASP.NET Core, and how do you serve them?

Static files are files that are not processed by the server (like HTML, CSS, JavaScript, and images). To serve static files in ASP.NET Core, use the UseStaticFiles middleware in the Configure method of Startup.cs. This middleware enables static files to be served from the web root (wwwroot) directory by default, but you can also configure it to serve files from other directories.

Describe the process of database migration in Entity Framework Core.

Database migration in Entity Framework Core involves using the EF Core tools to generate code that can update the database schema to match the current state of your model classes. This is done by creating a series of migration files that represent incremental changes to the database structure. You can apply migrations to update the database schema using the Update-Database command in the Package Manager Console or dotnet ef database update command in the CLI.

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

The ConfigureServices method in Startup.cs is used to configure services that will be used by the application through dependency injection. This includes configuring options for built-in services (like MVC, Entity Framework Core, and Identity), registering custom application services, and setting up configurations for aspects like logging, database contexts, and more.

How do you optimize the performance of an ASP.NET Core MVC application?

Optimizing the performance of an ASP.NET Core MVC application involves several strategies, including but not limited to, implementing response caching, minimizing the use of synchronous operations, optimizing database access and queries, using the latest version of .NET Core and ASP.NET Core, enabling gzip or Brotli compression for responses, optimizing static files delivery, and avoiding unnecessary middleware in the request pipeline. Monitoring and profiling the application can help identify and address specific performance bottlenecks.

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

If you want to share any questions and answers, please put them in the comment section, which will benefit others. If you face any questions in the interview that we are not covering here, please feel free to put that question(s) in the comment section, and we will definitely add that question(s) with answers as soon as possible.