.NET Core interview questions and answers

If you are working in .Net core and preparing for interviews, check out this article on .Net core interview questions and answers.

This article covers 25 critical .NET Core interview questions and detailed answers that encompass various aspects of the framework, ranging from basic concepts to more complex topics. The questions cover .NET Core basics, ASP.NET Core, the Command Line Interface, Middleware, Dependency Injection, Deployments, and much more.

Table of Contents

.NET Core interview questions and answers

Here are the best 35 .NET Core interview questions and answers.

Q-1: What is .NET Core

Ans: .NET Core is an open-source, general-purpose development platform maintained by Microsoft and the .NET community on GitHub. It’s cross-platform (supports Windows, macOS, and Linux) and can be used to build device, cloud, and IoT applications.

Q-2: How does .NET Core differ from the .NET Framework?

Ans: .NET Framework is Windows-only, while .NET Core is cross-platform. .NET Core is also modular, meaning that it has a smaller footprint as you only need to include the dependencies you need, compared to .NET Framework which comes as a large package.

Q-3: What is the purpose of .NET Standard?

Ans: .NET Standard is a specification of .NET APIs that all .NET platforms have to implement. It brings uniformity across the .NET frameworks (.NET Core, .NET Framework, Xamarin, etc.), enabling code sharing and reuse.

Q-4: Explain the .NET Core CLI

Ans: The .NET Core CLI (Command-Line Interface) is a powerful tool that allows developers to create, develop, run, and publish .NET Core applications. The CLI commands are consistent across different platforms.

Q-5: What is Middleware in .NET Core?

Ans: Middleware in .NET Core is software that is assembled into an application pipeline to handle requests and responses. Each piece of middleware can either handle the request completely or pass it on to the next piece of middleware in the pipeline.

Q-6: What is Dependency Injection in .NET Core?

Ans: Dependency Injection (DI) is a design pattern that enables loose coupling of code, making it more modular and testable. .NET Core includes built-in support for DI.

Q-7: What are the different types of Deployments in .NET Core?

Ans: .NET Core supports two types of deployments: Framework-dependent deployment (FDD) and Self-contained deployment (SCD). FDD requires the .NET Core runtime installed on the target machine while SCD does not.

Q-8: What is Kestrel in .NET Core?

Ans: Kestrel is a cross-platform web server for .NET Core based on the libuv library. It is typically run behind a production web server like Nginx or Apache.

Q-9: What are some key features of ASP.NET Core?

Ans: Some key features of ASP.NET Core include built-in support for dependency injection, logging, configuration, authentication, and authorization. It also supports development and deployment on multiple platforms.

Q-10: What is Razor Pages in ASP.NET Core?

Ans: Razor Pages is a feature of ASP.NET Core that makes coding page-focused scenarios easier and more productive. It’s a page-based programming model that makes building web UI easier and more productive.

Q-11: What is Entity Framework Core?

Ans: Entity Framework Core (EF Core) is a lightweight, extensible, open-source, and cross-platform version of the popular Entity Framework data access technology.

Q-12: What are the main advantages of .NET Core?

Some main advantages include cross-platform support, high performance, open-source, side-by-side versioning, and a flexible deployment model.

Q-13: What is the Startup class in .NET Core?

Ans: The Startup class is where you define the request handling pipeline and where any services needed by the app are configured.

Q-14: Explain the ConfigureServices and Configure methods in the Startup class

The ConfigureServices method is used to add services to the container that will be used for dependency injection and configuration. The Configure method is used to specify how the app will respond to HTTP requests.

Q-15: What are Tag Helpers in ASP.NET Core?

Tag Helpers in ASP.NET Core enable server-side code to participate in creating and rendering HTML elements in Razor files. They provide a cleaner and more HTML-like syntax for Razor views.

Q-16: What is the difference between AddSingleton, AddScoped, and AddTransient in ASP.NET Core?

These methods are used for setting up the services for dependency injection with different lifetimes. AddSingleton creates a single instance for the entire application lifecycle. AddScoped creates an instance per client request. AddTransient creates a new instance every time a service instance is requested.

Q-17: How does the Program.cs file work in a .NET Core application?

The Program.cs file in a .NET Core application is the entry point of the application. It includes a Main method that sets up a host with defaults and builds and runs the application.

Q-18: What is IHost and IHostBuilder in .NET Core?

IHost and IHostBuilder are interfaces for implementing a Host. A host is responsible for app startup and lifetime management. The host configures app configuration, logging, dependency injection, and the web server.

Q-19: What is Blazor in .NET Core?

Blazor is a framework in .NET Core for building interactive client-side web UI with .NET. It allows you to run .NET in the browser via WebAssembly.

Q-20: How do you handle errors in ASP.NET Core?

Errors in ASP.NET Core can be handled using middleware, custom error handling services, or filters. A developer exception page can be added during development to view detailed information about the exceptions.

Q-21: What is SignalR in .NET Core?

SignalR is a library in .NET Core for building real-time, multi-user interactive web applications. It provides a simple API for creating server-to-client remote procedure calls (RPC) that call JavaScript functions in client browsers from server-side .NET Core code.

Q-22: What is the difference between .NET Core 3.1 and .NET 5?

.NET 5 is the next step forward with .NET Core and aims to unify the .NET platform across all types of apps. It has improved performance, a smaller container image size, and single file applications. .NET Core 3.1 is a long-term support (LTS) version and will be supported until at least December 2022.

Q-23: What are some new features in C# 8.0?

C# 8.0 introduced several new features including Nullable Reference Types, Asynchronous Streams, Ranges and Indices, Pattern Matching Enhancements, and Default Interface Members.

Q-24: What is a Worker Service in .NET Core?

A Worker Service in .NET Core is a type of project template used to create long-running services or background tasks, similar to Windows services or Linux daemons.

Q-25: How do you create a Web API in .NET Core?

To create a Web API in .NET Core, you create a new project using the ‘API’ template, define a model class, a database context, a controller, and then configure the database connection in the Startup class. The controller uses Entity Framework Core to perform CRUD operations on the database.

Q-26: What is the syntax to create a new .NET Core project from the command line?

The command to create a new .NET Core project from the command line is: dotnet new console -n YourProjectName.

Q-27: How do you add a package reference to your .NET Core project using the .NET Core CLI?

To add a package reference, you can use the command: dotnet add package PackageName.

Q-28: Write a code snippet to register a transient dependency in .NET Core

public void ConfigureServices(IServiceCollection services)
{
    services.AddTransient<IMyService, MyService>();
}

Q-29: How do you inject a service into a .NET Core controller?

You can use constructor injection to inject services into a controller, as shown below:

public class MyController : Controller
{
    private readonly IMyService _myService;

    public MyController(IMyService myService)
    {
        _myService = myService;
    }
}

Q-30: How can you create a custom Middleware in .NET Core?

You can create a custom middleware by creating a class with a method called Invoke or InvokeAsync. This method gets an HttpContext object and calls the next middleware in the pipeline.

public class MyMiddleware
{
    private readonly RequestDelegate _next;

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

    public async Task InvokeAsync(HttpContext httpContext)
    {
        // Your code here

        await _next(httpContext);
    }
}

Q-31: Write a code snippet to read configuration settings in .NET Core

Below is the code to read configuration settings in .Net core.

public class MyController : Controller
{
    private readonly IConfiguration _configuration;

    public MyController(IConfiguration configuration)
    {
        _configuration = configuration;
    }

    public IActionResult Index()
    {
        string setting = _configuration["MySetting"];

        // Rest of your action logic

        return View();
    }
}

Q-32: How do you handle exceptions globally in ASP.NET Core?

In the Startup class, in the Configure method, you can use the UseExceptionHandler middleware to handle exceptions globally.

public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
    if (env.IsDevelopment())
    {
        app.UseDeveloperExceptionPage();
    }
    else
    {
        app.UseExceptionHandler("/Home/Error");
    }
    // Rest of your middleware setup
}

Q-33: Write a code snippet for defining a simple Model in .NET Core

public class Employee
{
    public int Id { get; set; }
    public string Name { get; set; }
    public string Department { get; set; }
}

Q-34: How can you serve static files in ASP.NET Core?

In the Configure method of the Startup class, use the UseStaticFiles middleware.

public void Configure(IApplicationBuilder app)
{
    app.UseStaticFiles();

    // Rest of your middleware setup
}

Q-35: How do you create an ASP.NET Core Web API action to respond to HTTP GET requests?

Below is the code to create an ASP.NET Core Web API action to respond to HTTP GET requests.

[Route("api/[controller]")]
[ApiController]
public class MyController : ControllerBase
{
    [HttpGet]
    public IActionResult Get()
    {
        // Your logic here

        return Ok();
    }
}

.NET Core interview questions and answers

Conclusion

Having a solid understanding of .NET Core is essential for any software developer aiming to excel in the industry today. With its cross-platform capabilities and high performance, .NET Core is a sought-after framework that organizations are heavily investing in. Consequently, the demand for skilled .NET Core professionals is high.

By familiarizing yourself with these 25 key .NET core interview questions, you can confidently step into your next interview with the knowledge and understanding necessary to impress your prospective employer. Remember, the learning doesn’t stop here. Always keep yourself updated with new releases and enhancements in the .NET Core framework to stay ahead in your career.