ASP.NET Core MVC Intermediate Interview Questions and Answers

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ASP.NET Core MVC Intermediate Interview Questions and Answers

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

How do you use the IConfiguration interface in ASP.NET Core?

The IConfiguration interface in ASP.NET Core is used to read settings from various configuration sources like appsettings.json, environment variables, command-line arguments, etc. It is typically injected into classes using Dependency Injection. You can access specific configuration values by using the GetSection, GetValue<T>, or indexing ([“Section:Subsection:Key”]) methods.

What is Model Validation in ASP.NET Core MVC, and how is it implemented?

Model Validation in ASP.NET Core MVC ensures that incoming data adheres to the expected format and rules before a controller action is executed. It is implemented using Data Annotations on model properties (e.g., [Required], [StringLength(50)]) and the ModelState.IsValid checks within a controller action to verify if the model passed to the action meets all validation rules.

Explain the role and use of the app.UseMvc() middleware.

The app.UseMvc() middleware is used in the ASP.NET Core request pipeline to enable MVC (Model-View-Controller) capabilities. It configures routing for MVC and API controllers. With ASP.NET Core 3.x and later, the recommended approach is to use app.UseEndpoints(endpoints => { endpoints.MapControllerRoute(…); }) instead for more flexible routing.

How can you implement Dependency Injection without the built-in container in ASP.NET Core?

To implement Dependency Injection without the built-in container, you can integrate a third-party container like Autofac or StructureMap. This involves setting up the third-party container in the ConfigureServices method of the Startup class and then using the container’s specific methods to register and resolve dependencies.

Describe the process of implementing a custom Tag Helper in ASP.NET Core.

Implementing a custom Tag Helper involves creating a class that inherits from TagHelper and overriding the Process or ProcessAsync method to manipulate the output. The class must be decorated with the [HtmlTargetElement] attribute to define which HTML elements it targets. Finally, add the Tag Helper to the view using the @addTagHelper directive.

What are the differences between ActionResult and IActionResult?

ActionResult is an abstract class that can represent various HTTP responses (e.g., ViewResult, FileResult). IActionResult is an interface that ActionResult and other non-ActionResult types (like JsonResult) implement, providing a more flexible way to return different types of responses from controller actions.

How do you manage application settings and configurations across different environments?

ASP.NET Core uses an environment-based configuration system where you can have different appsettings files (e.g., appsettings.Development.json, appsettings.Production.json) for different environments. The appropriate settings file is selected based on the current environment, which can be set through the ASPNETCORE_ENVIRONMENT environment variable.

Explain the concept of Razor Pages in ASP.NET Core.

Razor Pages is a page-based programming model that makes building web UI easier and more productive. Razor Pages are built on top of MVC, and each page is associated with a page model class. It simplifies the web application structure by eliminating the need for a separate controller.

How do you use Data Annotations in ASP.NET Core?

Data Annotations are used in ASP.NET Core to provide declarative data validation and formatting over model properties. You can annotate model properties with attributes like [Required], [EmailAddress], [Range], etc., to specify the rules that the data must conform to.

What is the purpose of the launchSettings.json file?

The launchSettings.json file in ASP.NET Core projects specifies the configuration settings used by Visual Studio and the dotnet run command for launching the application. It includes settings for different environments, such as development, staging, and production, and can specify environment variables, application URLs, and other launch parameters.

Describe how to implement social authentication in ASP.NET Core.

To implement social authentication, you first need to register your application with the social identity providers (e.g., Google, Facebook, Twitter) to obtain the client ID and secret. Then, in your ASP.NET Core application, configure the authentication middleware using services.AddAuthentication().AddGoogle() or similar methods in the ConfigureServices method of your Startup class, passing in the client ID and secret.

How do you perform database seeding in Entity Framework Core?

Database seeding in Entity Framework Core can be performed by overriding the OnModelCreating method in your DbContext class and using the modelBuilder.Entity<Type>().HasData() method to specify the seed data. Alternatively, you can create a custom migration that includes SQL commands to insert the initial data into the database.

What is the role of the ConfigureServices method in the Startup class?

The ConfigureServices method in the Startup class is where you register services needed by your application with the dependency injection container. ASP.NET Core comes with built-in support for dependency injection, allowing you to add application services to the container and then consume them in your application via constructor injection. Services like Entity Framework contexts, MVC/Razor page services, logging, and many others are configured here.

Explain the significance of the async and await keywords in ASP.NET Core MVC actions.

The async and await keywords are used to make asynchronous operations in .NET. In the context of ASP.NET Core MVC actions, they allow for non-blocking I/O operations, enhancing the scalability of web applications by freeing up threads to serve other requests while waiting for I/O operations like database calls or API requests to complete. This leads to better resource utilization and the ability to handle more concurrent requests.

How do you configure and use static files in ASP.NET Core applications?

Static files (like HTML, CSS, JavaScript, and images) are served through the Static File Middleware in ASP.NET Core. To use static files, you need to add the middleware to your application’s request processing pipeline using the UseStaticFiles extension method in the Configure method of your Startup class. You can also configure options to serve static files from specific folders or to enable directory browsing.

What are environment tags in ASP.NET Core?

Environment tags, specifically <environment> tags in Razor views, allow you to conditionally render content based on the hosting environment (e.g., Development, Staging, Production). This is useful for including different scripts or stylesheets depending on whether the application is in development or production.

Describe the process of creating and using a custom middleware component.

Creating a custom middleware in ASP.NET Core involves defining a class with the Invoke or InvokeAsync method that takes HttpContext as a parameter and optionally returns a Task. The middleware can then be added to the application’s request processing pipeline using the UseMiddleware<> extension method in the Configure method of the Startup class. Middleware components can handle requests, terminate them, or pass them to the next component in the pipeline.

How do you implement API authentication using JWT in ASP.NET Core?

To implement JWT (JSON Web Tokens) authentication in ASP.NET Core, you first need to configure the JWT authentication scheme by adding it to the service collection in the ConfigureServices method using the AddAuthentication method. You specify the token parameters like issuer, audience, and the key used to sign the token. Then, apply the [Authorize] attribute to your controllers or actions where you want to enforce authentication.

Explain the use of IOptions to access configuration settings.

IOptions is an interface in ASP.NET Core that allows you to access strongly typed settings from configuration sources (like appsettings.json, environment variables). You define a class that matches the configuration structure and then register it with the dependency injection container using the Configure method. This way, you can inject IOptions<T> into your classes, where T is your configuration class, to access the settings.

What is the difference between AddMvc() and AddMvcCore() extensions?

AddMvc() and AddMvcCore() are extension methods used to register MVC services in the application’s service container. AddMvc() adds all the essential MVC services plus additional features like Razor Pages, Authorization, and Data Annotations. AddMvcCore() adds only the core MVC services, allowing for more fine-grained control over the services you include in your application, which can be beneficial for performance or when you need a minimal setup.

How do you handle multiple environments in ASP.NET Core, such as development, staging, and production?

ASP.NET Core uses the IWebHostEnvironment interface to provide information about the web hosting environment. You can inject IWebHostEnvironment into your classes and use it to conditionally execute code based on the EnvironmentName property. Additionally, ASP.NET Core supports environment-specific configuration files (e.g., appsettings.Production.json) and environment variables to configure the application differently across environments.

Describe how to use the [ValidateAntiForgeryToken] attribute.

The [ValidateAntiForgeryToken] attribute is used to prevent cross-site request forgery (CSRF) attacks. When applied to an action method, a request must include a valid anti-forgery token. This token is automatically included in forms generated using the form tag helper or the Html.AntiForgeryToken() helper in Razor views. The validation of the token ensures that the request originates from the same site, protecting against CSRF attacks.

How do you customize and handle logging in ASP.NET Core?

ASP.NET Core uses a logging API that works with various logging providers (like console, debug, EventSource, and third-party loggers). You can configure logging in the ConfigureServices method of the Startup class by calling AddLogging and setting up the desired logging providers and filters. You can also create custom logging providers by implementing the ILoggerProvider interface.

What are some common performance optimizations in ASP.NET Core applications?

Common performance optimizations in ASP.NET Core include:

• Using response caching to reduce the number of requests that need to be fully processed.
• Minimizing the use of synchronous operations to avoid blocking threads.
• Implementing asynchronous I/O operations for data access and external calls.
• Optimizing static file delivery through response compression and caching headers.
• Reducing the use of middleware components that are not necessary for processing certain requests.

Explain how to secure APIs in ASP.NET Core.

Securing APIs in ASP.NET Core can be achieved through various methods, including:

• Implementing authentication and authorization using JWT, OAuth, or OpenID Connect.
• Using HTTPS to encrypt data in transit.
• Applying the [Authorize] attribute to controllers and actions to enforce access controls.
• Validating input to protect against SQL injection and XSS attacks.
• Use CORS (Cross-Origin Resource Sharing) policies to control how your API is accessed from different origins.

What is Endpoint Routing in ASP.NET Core 3.0 and above?

Endpoint Routing was introduced in ASP.NET Core 3.0 to enable more efficient routing decisions and to provide a mechanism to configure routing information directly on the endpoints. It allows for more granular control over how requests are routed to different handlers and supports the application of middleware based on routing information. It improves the performance of routing decisions and makes the routing system more flexible and extensible.

Describe how to implement custom validation attributes.

Custom validation attributes in ASP.NET Core can be implemented by inheriting from the ValidationAttribute class and overriding the IsValid method. The IsValid method contains the logic to validate the input value. You can also add error messages and other validation logic within this method. Once implemented, the custom validation attribute can be applied to model properties to enforce custom validation rules.

How do you handle exceptions globally in ASP.NET Core MVC?

Global exception handling in ASP.NET Core MVC can be achieved by configuring the middleware pipeline to use the built-in UseExceptionHandler extension method. This method can redirect to a specified path or to an error-handling controller action when an unhandled exception occurs. Additionally, for more granular control, you can implement an IExceptionFilter or use the UseDeveloperExceptionPage method during development for detailed error information.

What is the purpose of the IWebHostEnvironment interface?

The IWebHostEnvironment interface provides information about the web hosting environment in which an application runs. It includes properties for accessing the application’s content root and webroot paths and helps to determine the environment name (e.g., Development, Staging, Production). This is useful for configuring services and behaviors differently based on the environment.

Explain how to use configuration providers in ASP.NET Core.

Configuration providers in ASP.NET Core are used to read configuration settings from various sources (e.g., files, environment variables, command-line arguments). You can use these providers by adding them to the configuration builder in the Startup class. ASP.NET Core supports a variety of configuration providers, and you can also implement custom providers if needed. The configuration system is hierarchical, allowing for settings to be overridden by different sources.

How do you manage user roles and permissions in ASP.NET Core?

User roles and permissions in ASP.NET Core can be managed using the built-in Identity framework. This framework provides support for role-based authorization, where you can assign users to roles and then apply authorization policies based on these roles. You can also implement more complex permission systems by extending the Identity framework or integrating with third-party services.

Describe how to configure CORS policies in services.

Cross-Origin Resource Sharing (CORS) policies in ASP.NET Core can be configured in the Startup class by using the AddCors method in the ConfigureServices method. You can define named CORS policies with specific settings (e.g., allowed origins, headers, methods) and then apply these policies globally or on a per-endpoint basis using the UseCors middleware.

How do you implement file download functionality in ASP.NET Core?

File download functionality in ASP.NET Core can be implemented by returning a FileResult from an action method. You can use the File method to generate this result, specifying the file’s content, content type, and file name. This method supports serving files from the file system, a byte array, or a stream.

What is the significance of the _ViewImports.cshtml file?

The _ViewImports.cshtml file is used to define common Razor directives that are imported into every Razor view in the same directory and its subdirectories. It can include @using statements for namespaces, @inject directives for dependency injection, and @addTagHelper directives. This file helps to reduce code duplication across views.

Explain the use of appsettings.json and how to access its values.

appsettings.json is a JSON configuration file in ASP.NET Core used to store application settings, such as connection strings, logging configuration, and custom application settings. You can access its values anywhere in your application by injecting the IConfiguration interface and using it to retrieve settings using the GetValue<T>, GetSection, or the indexer [] methods. Settings can be organized into hierarchical sections to group related settings together.

How do you implement custom logging providers in ASP.NET Core?

To implement a custom logging provider in ASP.NET Core, you need to create a class that implements the ILoggerProvider interface and possibly another class that implements the ILogger interface. The provider class is responsible for creating instances of your logger class. You then register your custom provider with the logging system by calling the AddProvider method on the ILoggingBuilder instance, which can be accessed in the ConfigureLogging method of the WebHostBuilder or the ConfigureServices method in the Startup class. Your logger class should contain the logic for storing or displaying log messages as required by your application.

Describe the process to create and use extension methods in ASP.NET Core.

Extension methods allow you to add new methods to existing types without modifying them. In ASP.NET Core, you might create extension methods for IApplicationBuilder, IServiceCollection, or other core types to simplify configuration or add custom functionality.

• To create an extension method, define a static class and method, with the first parameter being this, followed by the type you’re extending. For example, extending IApplicationBuilder for custom middleware.
• To use an extension method, simply call it on an instance of the type you’ve extended as if it were an instance method.

What are the best practices for securing sensitive data in ASP.NET Core applications?

• Use the Data Protection API to encrypt sensitive data.
• Store secrets securely using mechanisms like environment variables, Azure Key Vault, or the Secret Manager tool during development.
• Use HTTPS to secure data in transit.
• Implement secure authentication and authorization.
• Regularly update dependencies to mitigate vulnerabilities.

How do you use attribute routing in ASP.NET Core?

Attribute routing enables specifying routes directly on controllers and actions by using attributes. To use it, apply the [Route], [HttpGet], [HttpPost], etc., attributes to controllers and actions, specifying the template strings that define URLs.

What is the difference between UseAuthentication, UseAuthorization, and UseSession middleware?

• UseAuthentication adds the authentication middleware to the request pipeline, which authenticates users.
• UseAuthorization adds authorization middleware, which authorizes users based on the authentication performed earlier in the pipeline.
• UseSession adds session middleware, allowing for storing user data between requests. Sessions differ from authentication and authorization but can be used in conjunction with them to maintain user state.

How do you implement background tasks in ASP.NET Core?

Use hosted services or background tasks with IHostedService or BackgroundService. These services can be registered in the application’s service container and are started and stopped with the application.

Explain the purpose and use of the Health Checks API in ASP.NET Core.

The Health Checks API is used to check the health of an application and its dependencies, such as databases and external services. It’s useful for automated monitoring and readiness/liveness checks in microservices architectures. You implement health checks by registering them in the startup configuration and accessing them via a specified endpoint.

How do you deploy an ASP.NET Core application to a Linux server?

Deployment typically involves:

• Publishing the application from the development environment.
• Transferring the published application to the Linux server.
• Setting up a web server like Nginx or Apache as a reverse proxy to forward requests to the Kestrel web server used by ASP.NET Core.
• Configuring the server and application for production, including environment variables, logging, and service management (e.g., using systemd).

What are the benefits and scenarios for using SignalR in an application?

SignalR facilitates adding real-time web functionality, enabling server-side code to push content to clients instantly. It’s ideal for chat applications, real-time dashboards, notifications, and any scenario where you need instant communication between the server and clients.

How do you configure HTTPS and SSL in ASP.NET Core?

Configuring HTTPS and SSL involves:

• Acquiring an SSL certificate from a Certificate Authority (CA).
• Configuring the web server (e.g., Kestrel, IIS, Nginx) to use the certificate.
• Enforcing HTTPS in your application by using the UseHttpsRedirection middleware.

What is Response Caching, and how do you implement it?

Response caching reduces the number of requests a server must process by storing copies of previously requested resources. Implement it using the ResponseCaching middleware and configure caching settings with attributes like [ResponseCache] on controllers or actions.

Describe how to use the ProblemDetails class to handle API errors.

ProblemDetails is a class for representing errors in a machine-readable format. It’s used with the IActionResult returned from controllers to provide detailed error information in a standardized way, making it easier for clients to understand and handle errors.

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

• AddSingleton() creates a single instance of the service for the application’s lifetime.
• AddScoped() creates an instance of the service for each request.
• AddTransient() creates a new instance of the service each time it is requested.

How do you implement real-time web functionality using SignalR in ASP.NET Core?

Implementing real-time functionality with SignalR involves:

• Adding the SignalR library to your project.
• Creating a hub class that extends Hub, which acts as a high-level pipeline handling client-server communication.
• Configuring SignalR routes in your startup class.
• Connecting clients to the hub using the SignalR JavaScript client or other client SDKs, allowing for two-way communication between the server and connected clients.

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

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