Interview question and answer with full explanation and code example on .Net Core

Interview question and answer with a full explanation and code example on .Net Core

Here are 10 commonly asked interview questions about .NET Core along with their explanations and code examples. Please note that this is not an exhaustive list, but it covers some important topics:

Question 1: What is .NET Core? 

Explanation: .NET Core is a free and open-source, cross-platform framework for building modern applications. It allows you to develop and run applications on Windows, macOS, and Linux.

Question 2: What are the advantages of using .NET Core? 

Explanation: 

Some advantages of using .NET Core include:

• Cross-platform support
• Improved performance
• Smaller deployment package size
• Easy containerization with Docker
• Support for microservices architecture

Question 3: How do you create a new .NET Core project using the command line? 

Explanation: 

To create a new .NET Core project, you can use the following command:

arduino
dotnet new <template> -n <project-name>

For example, to create a new console application, you can use:

javascript
dotnet new console -n MyConsoleApp

Question 4: How do you handle dependencies in .NET Core? 

Explanation:

 .NET Core uses a built-in dependency injection (DI) framework to handle dependencies. You can register dependencies in the Startup class' ConfigureServices method using the AddTransient, AddScoped, or AddSingleton methods. For example:

csharp
services.AddTransient<IMyService, MyService>();

This registers MyService as a transient dependency, meaning a new instance will be created every time it's requested.

Question 5: How do you configure middleware in .NET Core? 

Explanation: 

Middleware can be configured in the Configure method of the Startup class using the Use extension methods. For example, to use the Authentication middleware:

csharp
app.UseAuthentication();

This ensures that the authentication middleware is executed for each incoming request.

Question 6: What is the difference between .NET Framework and .NET Core? 

Explanation: 

.NET Framework is a Windows-only framework, while .NET Core is cross-platform. .NET Core is also modular and lightweight compared to the monolithic .NET Framework. Additionally, .NET Core has a smaller deployment footprint and provides better performance.

Question 7: How do you handle routing in .NET Core? 

Explanation: 

Routing can be configured in the Configure method of the Startup class using the UseRouting and UseEndpoints methods. For example:

csharp

app.UseRouting();

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

This sets up routing for controllers in an ASP.NET Core application.

Question 8: How do you implement logging in .NET Core? 

Explanation:

 .NET Core provides a built-in logging framework called Microsoft.Extensions.Logging. You can add logging providers, such as console or file, in the ConfigureServices method of the Startup class. For example:

csharp
services.AddLogging(builder =>
{
    builder.AddConsole();
    builder.AddFile("logs/myapp-{Date}.txt");
});

This configures console and file logging providers.

Question 9: How do you work with databases in .NET Core? 

Explanation:

 .NET Core supports multiple database providers, such as SQL Server, MySQL, and SQLite. You can use Entity Framework Core (EF Core) as an ORM to work with databases. First, you need to install the relevant NuGet package for your chosen database provider. Then, you can create a DbContext and define entities and their relationships. Finally, you can use EF Core to perform CRUD operations on the database.

Question 10: How do you deploy a .NET Core application?

Explanation: 

There are multiple ways to deploy a .NET Core application, including self-contained deployment (SCD) and framework-dependent deployment (FDD). In SCD, you publish the application along with the .NET Core runtime, making it independent of the target system's installed runtime. In FDD, you publish only the application, assuming the target system already has the required .NET Core runtime installed. You can use tools like Docker, Azure, or AWS for containerization and cloud deployment.

These questions cover a range of important topics related to .NET Core. Remember to customize your answers based on your own experience and knowledge.

Question 11: What is ASP.NET Core? 

Explanation: 

ASP.NET Core is a cross-platform framework for building web applications. It is a part of the .NET Core platform and provides a modular, high-performance, and scalable environment for developing web applications.

Question 12: What is the difference between ASP.NET Core and ASP.NET? 

Explanation: 

ASP.NET Core is a complete rewrite of ASP.NET, designed to be cross-platform, modular, and lightweight. It has a more flexible architecture and improved performance compared to ASP.NET.

Question 13: How do you create a new ASP.NET Core project using the command line? 

Explanation: 

To create a new ASP.NET Core project, you can use the following command:

arduino
dotnet new web -n <project-name>

For example, to create a new ASP.NET Core web application, you can use:

arduino
dotnet new web -n MyWebApp

Question 14: What is the difference between Razor Pages and MVC in ASP.NET Core? 

Explanation: 

Razor Pages and MVC are two approaches to building web applications in ASP.NET Core. Razor Pages is a lightweight framework for building page-centric web applications, while MVC (Model-View-Controller) is a more comprehensive framework that separates concerns into models, views, and controllers.

Question 15: How do you handle authentication and authorization in ASP.NET Core? 

Explanation: 

ASP.NET Core provides built-in middleware for handling authentication and authorization. You can configure authentication schemes and policies in the Startup class' ConfigureServices method and use the Authorize attribute to enforce authorization on controllers or actions. You can also use external identity providers like Azure AD or OAuth for authentication.

Question 16: What is the purpose of the appsettings.json file in ASP.NET Core? 

Explanation: 

The appsettings.json file is used to store application-specific configuration settings. It allows you to separate configuration from code and provides a structured way to configure various aspects of your application, such as database connections, logging settings, or custom application settings.

Question 17: How do you read configuration settings from the appsettings.json file in ASP.NET Core? 

Explanation: 

Configuration settings from the appsettings.json file can be accessed through the Configuration property of the WebHostBuilder or IConfiguration interface. For example, to read a connection string, you can use the following code:

csharp
string connectionString = Configuration.GetConnectionString("DefaultConnection");

Question 18: What is dependency injection (DI) and how is it implemented in ASP.NET Core? 

Explanation: 

Dependency injection is a design pattern used to provide dependencies to an object rather than creating them directly within the object. In ASP.NET Core, the built-in DI container is used to manage dependencies. Dependencies can be registered in the Startup class' ConfigureServices method and injected into controllers or other components using constructor injection.

Question 19: How do you enable CORS (Cross-Origin Resource Sharing) in ASP.NET Core? 

Explanation: 

To enable CORS in ASP.NET Core, you can add the UseCors middleware in the Configure method of the Startup class. For example, to allow all origins, headers, and methods, you can use the following code:

csharp
app.UseCors(builder => builder.AllowAnyOrigin().AllowAnyHeader().AllowAnyMethod());

Question 20: How do you handle exceptions in ASP.NET Core? 

Explanation: 

ASP.NET Core provides a global exception handling mechanism through middleware. You can use the UseExceptionHandler or UseStatusCodePages middleware to handle exceptions and provide appropriate responses to the client. Additionally, you can create custom exception filters or use logging frameworks to handle exceptions.

Question 21: What is middleware in ASP.NET Core? 

Explanation: 

Middleware is software that sits between the server and your application, processing requests and generating responses. Middleware can perform tasks such as routing, authentication, logging, or exception handling. It allows you to modularize your application's behavior and apply cross-cutting concerns.

Question 22: How do you implement caching in ASP.NET Core? 

Explanation: 

ASP.NET Core provides built-in support for caching through the IMemoryCache interface. You can register the cache service in the Startup class' ConfigureServices method and then use it to cache expensive operations or frequently accessed data. Here's an example:

csharp
public class MyService
{
    private readonly IMemoryCache _cache;

    public MyService(IMemoryCache cache)
    {
        _cache = cache;
    }

    public string GetData()
    {
        return _cache.GetOrCreate("myKey", entry =>
        {
            // Expensive operation to fetch data
            return FetchData();
        });
    }
}

Question 23: What is the role of the IWebHostEnvironment interface in ASP.NET Core? 

Explanation: 

The IWebHostEnvironment interface provides information about the web host's environment, such as the content root path, the environment name (development, production, etc.), or whether the application is running in a development environment or not.

Question 24: How do you perform logging in ASP.NET Core? 

Explanation: 

ASP.NET Core uses the Microsoft.Extensions.Logging framework for logging. You can configure logging providers, such as console, debug, or file, in the ConfigureServices method of the Startup class. Logging can then be used in controllers or other components by injecting the ILogger<T> interface. Here's an example:

csharp
private readonly ILogger<MyController> _logger;

public MyController(ILogger<MyController> logger)
{
    _logger = logger;
}

public IActionResult Index()
{
    _logger.LogInformation("Processing Index action");
    return View();
}

Question 25: How do you implement custom middleware in ASP.NET Core? 

Explanation: 

Custom middleware can be implemented by creating a class that has a method with the signature Task InvokeAsync(HttpContext context). This method is responsible for processing the request and generating the response. The custom middleware can be added to the pipeline using the UseMiddleware<T> extension method. Here's an example:

csharp
public class MyMiddleware
{
    private readonly RequestDelegate _next;

    public MyMiddleware(RequestDelegate next)
    {
        _next = next;
    }

    public async Task InvokeAsync(HttpContext context)
    {
        // Perform custom logic before the next middleware
        await _next(context);
        // Perform custom logic after the next middleware
    }
}

// In Startup.Configure method
app.UseMiddleware<MyMiddleware>();

Question 26: How do you perform unit testing in ASP.NET Core? 

Explanation: 

ASP.NET Core provides a test framework called xUnit.net, along with other popular testing frameworks like NUnit or MSTest. You can write unit tests for controllers, services, or middleware using these frameworks. Additionally, you can use the TestServer or WebHostBuilder to create an in-memory test server for integration testing.

Question 27: What is Razor syntax in ASP.NET Core? 

Explanation: 

Razor is a markup syntax used to combine server-side code with HTML markup to create dynamic web pages. Razor syntax allows you to embed C# code within HTML using the @ symbol. It provides features like expressions, conditional statements, loops, and partial views.

Question 28: How do you use dependency injection in a Razor view in ASP.NET Core? 

Explanation: 

Dependency injection can be used in a Razor view by injecting dependencies through the view's constructor or using the @inject directive. Here's an example:

csharp
@inject MyService _myService

<h1>@_myService.GetTitle()</h1>

Question 29: How do you handle file uploads in ASP.NET Core? 

Explanation: 

File uploads can be handled in ASP.NET Core by using the IFormFile interface. You can include a file input field in your HTML form and then access the uploaded file in the corresponding controller action using model binding or the Request.Form.Files collection.

Question 30: What is Entity Framework Core (EF Core) in ASP.NET Core? Explanation: Entity Framework Core is an object-relational mapping (ORM) framework that allows you to work with databases using strongly typed entities. It provides a set of APIs for performing database operations, such as querying, inserting, updating, or deleting records, without writing raw SQL queries.

Question 31: How do you configure Entity Framework Core in ASP.NET Core? 

Explanation: 

Entity Framework Core can be configured in the ConfigureServices method of the Startup class. You need to register the DbContext and configure the database provider. Here's an example using SQL Server:

csharp
services.AddDbContext<ApplicationDbContext>(options =>
    options.UseSqlServer(Configuration.GetConnectionString("DefaultConnection")));

Question 32: How do you perform database migrations in Entity Framework Core? 

Explanation: 

Entity Framework Core migrations are used to manage changes to the database schema. You can create migrations using the dotnet ef migrations add command and apply them to the database using the dotnet ef database update command. Migrations allow you to evolve the database schema as your application changes over time.

Question 33: How do you perform eager loading in Entity Framework Core? 

Explanation: 

Eager loading is the process of loading related entities along with the main entity. In Entity Framework Core, you can use the Include method to specify related entities to be included in the query results. Here's an example:

csharp
var authors = context.Authors.Include(a => a.Books).ToList();

Question 34: How do you handle transactions in Entity Framework Core? 

Explanation: 

Entity Framework Core supports transactions through the DbContext class. You can use the BeginTransaction method to start a new transaction, and then perform database operations within the transaction scope. Here's an example:

csharp
using var transaction = context.Database.BeginTransaction();
try
{
    // Perform database operations
    context.SaveChanges();
    transaction.Commit();
}
catch
{
    transaction.Rollback();
    throw;
}

Question 35: How do you implement a custom authentication scheme in ASP.NET Core? 

Explanation: 

You can implement a custom authentication scheme in ASP.NET Core by creating a class that derives from AuthenticationHandler<TOptions> and implementing the necessary methods. You also need to register your authentication scheme in the ConfigureServices method of the Startup class. This allows you to integrate with custom authentication providers or protocols.

Question 36: How do you implement health checks in ASP.NET Core? 

Explanation: 

Health checks are used to monitor the health of an application's dependencies or components. In ASP.NET Core, you can implement health checks by creating custom health check classes that derive from IHealthCheck and registering them in the ConfigureServices method of the Startup class. The health checks can then be accessed using the /health endpoint.

Question 37: How do you implement background tasks or scheduled jobs in ASP.NET Core? 

Explanation: 

ASP.NET Core provides the IHostedService interface to implement background tasks or scheduled jobs. You can create a class that implements this interface and register it as a hosted service in the ConfigureServices method of the Startup class. The IHostedService implementation can then perform long-running tasks or scheduled jobs.

Question 38: How do you implement API versioning in ASP.NET Core? 

Explanation: 

API versioning allows you to have multiple versions of your API endpoints. In ASP.NET Core, you can implement API versioning by configuring the ApiVersioning middleware in the ConfigureServices method of the Startup class. You can define different versions of your API controllers using attributes or conventions.

Question 39: How do you implement distributed caching in ASP.NET Core? 

Explanation: 

Distributed caching allows you to cache data across multiple instances of your application or different servers. In ASP.NET Core, you can use distributed caching by registering a distributed cache implementation, such as Redis or SQL Server, in the ConfigureServices method of the Startup class. The distributed cache can then be used to store and retrieve data using cache keys.

Question 40: How do you handle concurrency in Entity Framework Core? 

Explanation: 

Entity Framework Core provides optimistic concurrency control by using a concurrency token, typically a Timestamp or RowVersion column in the database table. When updating a record, EF Core checks if the concurrency token has changed since the entity was retrieved. If the token has changed, it means that another process has modified the record, and EF Core throws a DbUpdateConcurrencyException. You can handle this exception by reloading the entity and applying the necessary logic to resolve the conflict.

These additional questions cover a broader range of topics related to .NET Core and ASP.NET Core. Remember to tailor your answers based on your own understanding and experience.