Top 25 .NET Core Interview Questions & Answers

1. Introduction

Navigating a job interview can be daunting, especially in the tech industry where proficiency and expertise are meticulously evaluated. When it comes to roles that require knowledge of .NET Core, preparing for the technical interview is crucial. This article is designed to guide you through the most common .net core interview questions you might encounter. Whether you’re an aspiring software developer or a seasoned engineer, mastering these questions will bolster your confidence and increase your chances of success.

2. Understanding .NET Core and Its Ecosystem

.NET Core represents a significant evolution in Microsoft’s .NET technology stack. It is an open-source, cross-platform framework that enables developers to build modern, cloud-based, internet-connected applications. Unlike the proprietary .NET Framework, .NET Core is designed to be agile, modular, and work across different platforms, which is why it’s become increasingly popular for enterprise-level software development.

In the context of job interviews, knowledge of .NET Core speaks to a candidate’s ability to work with current technologies and adapt to the ever-evolving landscape of software development. Proficiency in .NET Core indicates a developer’s understanding of not just coding, but also aspects of software architecture, security, and performance optimization. For organizations, candidates with strong .NET Core skills are invaluable in driving innovation and maintaining competitive in a dynamic market.

3. .NET Core Interview Questions

1. What is .NET Core and how does it differ from .NET Framework? (Framework Knowledge)

.NET Core is a free, open-source, cross-platform framework developed by Microsoft for building modern, cloud-based, and internet-connected applications such as web applications, IoT applications, and mobile backends. It is a complete rewrite of the .NET Framework, designed to be modular, lightweight, and work across different platforms, including Windows, macOS, and Linux.

The main differences between .NET Core and .NET Framework include:

• Cross-Platform: .NET Core supports cross-platform development, making it possible to run applications on different operating systems. In contrast, the .NET Framework is designed to run primarily on Windows.
• Modularity: .NET Core is modular, meaning you can include only the necessary packages in your application. The .NET Framework, on the other hand, is a monolithic framework that includes all features, whether needed or not.
• Open Source: .NET Core is an open-source framework, which allows the community to contribute and influence its development. The .NET Framework is closed source, with its development and updates managed by Microsoft.
• Performance: .NET Core offers improved performance over the .NET Framework due to optimizations and the ability to deploy only what you need.
• Side-by-Side Installation: .NET Core allows for multiple versions to be installed and run side by side on the same machine, which is particularly useful for managing different project dependencies and testing.
• Command-Line Interface: .NET Core comes with a powerful command-line interface (CLI) for creating, building, running, and publishing applications. This is a departure from the GUI-centric approach of the .NET Framework.

2. Why do you prefer using .NET Core for development? (Preference & Justification)

I prefer using .NET Core for development for several reasons:

• Cross-Platform Development: I can build applications that run on Windows, Linux, and macOS, which maximizes the potential user base and simplifies development and testing.
• Performance: .NET Core has significant performance improvements over the .NET Framework, which makes it suitable for high-performance applications.
• Microservices Architecture: The lightweight and modular nature of .NET Core aligns well with the microservices architecture, allowing me to build scalable and flexible applications.
• Modern Tooling: The introduction of a CLI and improved support for modern development practices, such as containerization with Docker, makes the development workflow more efficient.
• Continuous Improvements: Being an open-source platform, .NET Core benefits from community contributions and regular updates, which bring new features and enhancements frequently.

3. Can you explain the concept of middleware in .NET Core? (Middleware Concepts)

Middleware in .NET Core refers to software components that are assembled into an application pipeline to handle requests and responses. Each middleware component can perform operations before and after the next component in the pipeline. The concept of middleware allows developers to create a modular and extensible request pipeline, where different functionalities, such as authentication, logging, or error handling, can be added or removed with ease.

Here’s how middleware works in a .NET Core application:

public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
    if (env.IsDevelopment())
    {
        app.UseDeveloperExceptionPage();
    }

    app.UseRouting();

    app.UseAuthentication();
    app.UseAuthorization();

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

In the above example, the Configure method sets up the middleware components in the order they should execute. For instance, the UseRouting middleware is used to route requests to the appropriate endpoint, and UseAuthentication and UseAuthorization are used to handle authentication and authorization respectively.

4. How would you manage dependencies in a .NET Core project? (Dependency Management)

Managing dependencies in a .NET Core project is typically handled through the use of NuGet, the package manager for .NET. Dependencies are defined in the csproj file or via the Visual Studio NuGet package manager interface. Here’s how you can manage dependencies:

• Adding Dependencies: You can add dependencies using the dotnet add package command or through the NuGet Package Manager.
• Updating Dependencies: Dependencies can be updated to their latest version using the dotnet update package command or through the NuGet Package Manager.
• Removing Dependencies: Dependencies can be removed by using the dotnet remove package command or by manually editing the csproj file.
• Restoring Dependencies: Before building or running an application, you can restore all dependencies with the dotnet restore command to ensure all the necessary packages are downloaded and available.

Here is an example csproj snippet showing how dependencies are defined:

<ItemGroup>
    <PackageReference Include="Microsoft.AspNetCore.Mvc" Version="2.2.0" />
    <PackageReference Include="Newtonsoft.Json" Version="12.0.3" />
    <PackageReference Include="Swashbuckle.AspNetCore" Version="5.6.3" />
</ItemGroup>

5. What are Custom Tag Helpers in .NET Core and how do you use them? (Web Development)

Custom Tag Helpers in .NET Core are server-side code that participate in creating and rendering HTML elements in Razor files. They enable a cleaner, more maintainable, and expressive way to generate HTML content with server-side logic.

To use Custom Tag Helpers:

• Create a Custom Tag Helper: You define a class that inherits from TagHelper and override methods like Process or ProcessAsync to implement the desired functionality.
• Register the Tag Helper: In the _ViewImports.cshtml file, you add a directive to register your Tag Helper so that it can be used within your Razor views.
• Use the Tag Helper in Razor Views: You can then use your Custom Tag Helper in any Razor view by using the appropriate tag or attribute that corresponds to the Tag Helper you created.

Here is an example:

// CustomEmailTagHelper.cs
public class CustomEmailTagHelper : TagHelper
{
    public string MailTo { get; set; }

    public override void Process(TagHelperContext context, TagHelperOutput output)
    {
        output.TagName = "a"; // Replaces <custom-email> with <a> tag
        output.Attributes.SetAttribute("href", $"mailto:{MailTo}");
        output.Content.SetContent(MailTo);
    }
}

And in the _ViewImports.cshtml:

@addTagHelper *, Microsoft.AspNetCore.Mvc.TagHelpers
@addTagHelper *, YourAssemblyName // Register your custom Tag Helpers

Finally, using the Custom Tag Helper in a Razor view:

<custom-email mail-to="example@example.com"></custom-email>

This will generate the following HTML:

<a href="mailto:example@example.com">example@example.com</a>

6. How do you implement authentication and authorization in .NET Core applications? (Security)

Authentication in .NET Core can be implemented using various providers such as Identity, JWT (JSON Web Tokens), OAuth, etc. Authorization is the process of determining whether an authenticated user has access to a particular resource or operation. Here’s how to set them up:

Authentication:

• Set up the authentication service in Startup.ConfigureServices by calling services.AddAuthentication().
• Configure the authentication scheme with options, for example, by adding AddCookie, AddJwtBearer, or others depending on the method you want.
• Apply the [Authorize] attribute to controllers or actions to enforce authentication.

Authorization:

• Define policies via services.AddAuthorization in Startup.ConfigureServices.
• Use [Authorize(Policy = "PolicyName")] to enforce those policies on controllers or actions.
• Implement custom requirement handlers if you have complex authorization logic that can’t be expressed with built-in policies.

public void ConfigureServices(IServiceCollection services)
{
    services.AddAuthentication(JwtBearerDefaults.AuthenticationScheme)
            .AddJwtBearer(options =>
            {
                // Configure JWT Bearer with necessary parameters, like issuer, audience, and keys
            });

    services.AddAuthorization(options =>
    {
        options.AddPolicy("MustBeAdmin", policy => policy.RequireRole("Admin"));
    });
}

[Authorize(Policy = "MustBeAdmin")]
public class AdminController : ControllerBase
{
    // Controller actions
}

7. What is the Startup class in .NET Core and what is its purpose? (Framework Structure)

The Startup class in .NET Core is the entry point for configuring the app services and the app’s request processing pipeline. The class includes two important methods:

• ConfigureServices(IServiceCollection services): This method is used to add services to the application’s dependency injection container. Services like MVC, Entity Framework, Identity, and others are configured here.

• Configure(IApplicationBuilder app, IWebHostEnvironment env): This method is used to define how the application handles HTTP requests. Middleware components are configured here in the order that they will handle requests and responses.

public class Startup
{
    public void ConfigureServices(IServiceCollection services)
    {
        // Add services to the container.
    }

    public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
    {
        // Configure the HTTP request pipeline.
    }
}

8. How do you handle exceptions in a .NET Core Web API? (Error Handling)

Exception handling in a .NET Core Web API can be managed by using middleware, filters, or custom exception handling services. Here’s a basic approach using middleware:

• Create a custom exception handling middleware.
• Use app.UseExceptionHandler in the Configure method to point to your custom error handling logic.
• Capture the exceptions, log them, and return an appropriate HTTP response.

public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
    app.UseExceptionHandler(errorApp =>
    {
        errorApp.Run(async context =>
        {
            context.Response.StatusCode = 500; // Internal Server Error
            context.Response.ContentType = "application/json";

            var exceptionHandlerFeature = context.Features.Get<IExceptionHandlerFeature>();
            if (exceptionHandlerFeature != null)
            {
                var ex = exceptionHandlerFeature.Error;
                // Log the exception
                await context.Response.WriteAsync(ex.Message);
            }
        });
    });

    // Other configurations...
}

9. What is Entity Framework Core and how does it differ from Entity Framework? (ORM & Data Access)

Entity Framework Core (EF Core) is an ORM (Object-Relational Mapper) framework for .NET Core applications. It lets developers work with a database using .NET objects, eliminating the need for most of the data-access code.

Feature	Entity Framework	Entity Framework Core
Cross-platform	No (Windows only)	Yes (Windows, macOS, Linux)
Performance	Good	Better (more lightweight and performant)
Modular	No	Yes (modular with extensible components)
Command Line Tools	Limited	Rich command-line tools (EF Core CLI)
Supported Databases	Several	More via third-party providers
Lifecycle	Legacy (not actively developed)	Actively developed
.NET Support	.NET Framework	.NET Core / .NET 5+

EF Core is more modern, lightweight, and has more features that cater to the needs of cross-platform and high-performance applications.

10. Can you explain the code-first approach in EF Core? (ORM & Data Modeling)

The code-first approach in EF Core is a method of data modeling where you define your database schema using C# classes. The database tables, relationships, and other constraints are inferred from these classes using migrations.

Steps involved in the code-first approach:

1. Define your model classes (entities).
2. Create a DbContext class that includes DbSet properties for each model.
3. Use migrations to create/update the database schema based on your model classes.

public class BloggingContext : DbContext
{
    public DbSet<Blog> Blogs { get; set; }
    public DbSet<Post> Posts { get; set; }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        optionsBuilder.UseSqlServer(@"Server=(localdb)\mssqllocaldb;Database=Blogging;Integrated Security=True");
    }
}

public class Blog
{
    public int BlogId { get; set; }
    public string Url { get; set; }
    public List<Post> Posts { get; } = new List<Post>();
}

public class Post
{
    public int PostId { get; set; }
    public string Title { get; set; }
    public string Content { get; set; }
    public int BlogId { get; set; }
    public Blog Blog { get; set; }
}

After defining the model and context, you would create a migration and update the database using the following commands in the Package Manager Console:

Add-Migration InitialCreate
Update-Database

or in the CLI:

dotnet ef migrations add InitialCreate
dotnet ef database update

This approach allows for a very agile development process, as changes to the model can be easily propagated to the database through migrations.

11. How do you perform migrations in a .NET Core project? (Database Management)

To perform migrations in a .NET Core project, you would typically use Entity Framework Core (EF Core), which is an object-relational mapper (ORM) that enables .NET developers to work with a database using .NET objects. Here are the steps to perform migrations:

1. Define your database context and models: First, you have to define your database context class which derives from DbContext, and your model classes which represent the tables in your database.

2. Install necessary tools: Make sure you have the Entity Framework Core tools installed. This can be done by installing the Microsoft.EntityFrameworkCore.Tools NuGet package.

3. Initial migration: Create your initial migration by running the command dotnet ef migrations add InitialCreate in the terminal. This command scaffolds a migration to create the initial set of tables for the model.

4. Apply migrations: To apply the created migrations to the database, you use the command dotnet ef database update.

5. Subsequent migrations: If you make changes to your models, you need to create a new migration using the same dotnet ef migrations add command with a new name, and then apply it using the dotnet ef database update command.

Here’s a sample code for creating a DbContext and models:

public class BloggingContext : DbContext
{
    public DbSet<Blog> Blogs { get; set; }
    public DbSet<Post> Posts { get; set; }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        optionsBuilder.UseSqlServer(@"Server=(localdb)\mssqllocaldb;Database=Blogging;Integrated Security=True");
    }
}

public class Blog
{
    public int BlogId { get; set; }
    public string Url { get; set; }
    public List<Post> Posts { get; } = new List<Post>();
}

public class Post
{
    public int PostId { get; set; }
    public string Title { get; set; }
    public string Content { get; set; }
    public int BlogId { get; set; }
    public Blog Blog { get; set; }
}

12. What are the differences between AddSingleton, AddScoped, and AddTransient methods in .NET Core? (Dependency Injection)

The AddSingleton, AddScoped, and AddTransient methods in .NET Core’s dependency injection system define the lifetime of the services within the application. Here’s a comparison:

Method	Lifetime	Use Case
AddSingleton	Created once and shared across the entire application lifetime	State that is shared across the whole application, e.g., configuration root, logging, and object factory
AddScoped	Created once per client request	Services that need to be the same within a single request, e.g., database context, user-specific state
AddTransient	Created each time they’re requested	Lightweight, stateless services

AddSingleton

• This method creates a single instance of the service when the application starts and reuses that instance every time the service is requested.

AddScoped

• This method creates a new instance of the service for each client request (e.g., each HTTP request in a web application).

AddTransient

• This method creates a new instance of the service each time it is requested, regardless of whether it’s within the same request or across different requests.

13. How do you create and consume a NuGet package in a .NET Core project? (Package Management)

Creating a NuGet Package

1. Create a class library project if you haven’t already, and add the code you want to share as a NuGet package.
2. Edit the .csproj file to include necessary package metadata like the package id, version, authors, company, and description.
3. Run the command dotnet pack to generate the NuGet package file (.nupkg).
4. Publish the package to the NuGet gallery or your private repository using the dotnet nuget push command.

<PropertyGroup>
  <TargetFramework>netcoreapp3.1</TargetFramework>
  <PackageId>MyAwesomeLibrary</PackageId>
  <Version>1.0.0</Version>
  <Authors>YourName</Authors>
  <Company>YourCompany</Company>
  <Description>Your package description here.</Description>
</PropertyGroup>

Consuming a NuGet Package

1. Find the package you want to use on NuGet.org or your private repository.
2. Add the package to your project using the .NET CLI with dotnet add package PackageName, or use the NuGet Package Manager in Visual Studio.
3. Once the package is added to the project file, restore the packages using dotnet restore.
4. Use the package in your code by referencing it with using statements.

14. What is the purpose of the appsettings.json file in a .NET Core project? (Configuration)

The appsettings.json file in a .NET Core project is used for configuration. It typically contains settings that can vary between different environments, such as development, staging, and production. For example, it may include database connection strings, API keys, or application settings that need to be easily changed without the need for recompilation.

{
  "Logging": {
    "LogLevel": {
      "Default": "Warning"
    }
  },
  "ConnectionStrings": {
    "DefaultConnection": "Server=.;Database=MyApp;Trusted_Connection=True;"
  },
  "AppSettings": {
    "PageSize": 20
  }
}

You can access these settings in your application code using the IConfiguration service, which is typically injected into your classes through the constructor.

public class MyService
{
    private readonly string _connectionString;

    public MyService(IConfiguration configuration)
    {
        _connectionString = configuration.GetConnectionString("DefaultConnection");
    }
}

15. How do you use LINQ in .NET Core to query data? (Data Querying)

LINQ (Language Integrated Query) is a set of features in .NET that enables you to write powerful and flexible query expressions directly in C#. To use LINQ in .NET Core to query data, you can follow these steps:

1. Include necessary namespaces: Make sure to include the System.Linq namespace in your class file.

2. Create your data source: This could be a collection like List<T>, an array, or any IEnumerable<T> or IQueryable<T>.

3. Write your LINQ query: You can write LINQ queries using method syntax, query syntax, or a combination of both.

Here’s an example using a list of objects and querying it with LINQ:

using System;
using System.Collections.Generic;
using System.Linq;

public class Person
{
    public string Name { get; set; }
    public int Age { get; set; }
}

class Program
{
    static void Main()
    {
        List<Person> people = new List<Person>
        {
            new Person { Name = "Alice", Age = 30 },
            new Person { Name = "Bob", Age = 35 },
            new Person { Name = "Charlie", Age = 40 }
        };

        // Using query syntax
        var querySyntax = from person in people
                          where person.Age > 30
                          select person;

        // Using method syntax
        var methodSyntax = people.Where(p => p.Age > 30);

        foreach (var person in querySyntax)
        {
            Console.WriteLine(person.Name);
        }
    }
}

Both querySyntax and methodSyntax will yield the same result, filtering out the Person objects with an age greater than 30. The choice between query and method syntax is largely a matter of preference and readability in a given context.

16. Can you explain how Routing is handled in .NET Core MVC? (Web Development & Routing)

Routing in .NET Core MVC is the process by which incoming requests are matched to the routes defined in the application, which then determines the appropriate controller and action method to handle the request.

• Attribute routing: This method allows for more control by defining routes above the controller or the action methods using attributes. It is particularly useful when you need to define custom and complex routes directly within your controllers and actions. Here’s an example of attribute routing:

  [Route("api/[controller]")]
  public class ProductsController : Controller
  {
      [HttpGet("{id}")]
      public IActionResult GetProduct(int id)
      {
          // Implementation to return a product
      }
  }
  

• Conventional routing: This method is defined in the Startup.cs file and relies on a set of conventions that map URLs to controllers and actions. Conventional routing is often done using a pattern that identifies the controller, action, and parameters. Here’s an example of conventional routing:

  app.UseMvc(routes =>
  {
      routes.MapRoute(
          name: "default",
          template: "{controller=Home}/{action=Index}/{id?}");
  });
  

In .NET Core MVC 3.0 and later, Endpoint Routing is also available, which provides improved performance and enables advanced scenarios like gRPC.

17. How would you deploy a .NET Core application to a production environment? (Deployment)

Deployment of a .NET Core application can vary based on the hosting environment and the specific requirements of the application. Here are the common steps for deployment:

1. Publish the application: You can use the dotnet publish command, which compiles the application, reads through its dependencies specified in the .csproj file and publishes the resulting set of files to a directory.
2. Prepare the production environment: This may include setting up a web server such as IIS, Kestrel, or Nginx, as well as ensuring that any required services like a database server are available.
3. Configure environment-specific settings: Use appsettings.json, environment variables, or other configuration methods to set up production-specific settings.
4. Deploy the application: Depending on your hosting, you may deploy directly to a server via FTP/SFTP, use CI/CD pipelines, Docker containers, or cloud services like Azure App Service, AWS Elastic Beanstalk, etc.
5. Monitor and maintain: Once deployed, monitor the application’s performance and logs, and apply updates or patches as necessary.

18. Can you describe the role of a Controller in an MVC application? (MVC Pattern)

In an MVC (Model-View-Controller) application, the Controller plays the critical role of responding to user input and interactions. It acts as an intermediary between the Model, which represents the application’s data, and the View, which is the user interface.

• Request handling: Controllers receive HTTP requests and decide what to do with them.
• Model interaction: Controllers interact with models to retrieve data or carry out operations based on user input.
• Selecting views: Once the controller has processed data and applied business logic, it selects a view to render the user interface, passing any required data to it.
• Input validation: Controllers often perform input validation and enforce application logic before interacting with the model.
• ActionResult: Controllers return an ActionResult which can be a view, a file, a JSON response, or any other format depending on the request.

Here’s the basic structure of a controller:

public class HomeController : Controller
{
    public IActionResult Index()
    {
        return View();
    }
}

19. What are Global Query Filters in EF Core and how can they be used? (ORM & Data Access)

Global Query Filters in EF Core are LINQ query predicates applied to Entity Types in the model configuration. They automatically apply filters to all queries involving those entities. This feature is beneficial for concerns such as multi-tenancy, soft delete, or enabling/disabling entities globally.

Here’s how to use them:

• Defining a filter: A Global Query Filter is defined in the OnModelCreating method of your DbContext class using the HasQueryFilter method.

• Example: If you have a IsDeleted property on your entities to represent a soft delete, you can define a Global Query Filter to automatically exclude deleted entities from all queries.

  protected override void OnModelCreating(ModelBuilder modelBuilder)
  {
      modelBuilder.Entity<MyEntity>()
          .HasQueryFilter(e => !e.IsDeleted);
  }
  

• Overriding filters: In some cases, you may wish to access entities that are normally filtered out, such as in an administrative scenario. You can override the Global Query Filter for a specific query using the IgnoreQueryFilters method.

20. How do you implement logging in a .NET Core application? (Logging & Diagnostics)

In .NET Core, logging can be implemented using the built-in ILogger interface, which is a part of the Microsoft.Extensions.Logging namespace. You can configure logging in the Startup class and then inject ILogger into your classes where logging is needed.

• Configuration: Configure the logging providers in the ConfigureServices method of your Startup.cs file. You can add console, debug, event source, and other logging providers.
• Usage: Once configured, you can inject an ILogger or ILogger<T> where T is the class into which you are injecting the logger.

Here’s an example of setting up and using logging:

public void ConfigureServices(IServiceCollection services)
{
    services.AddLogging(configure => configure.AddConsole())
            .Configure<LoggerFilterOptions>(options => options.MinLevel = LogLevel.Information);
}

public class MyService
{
    private readonly ILogger<MyService> _logger;

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

    public void MyMethod()
    {
        _logger.LogInformation("Executing MyMethod");
    }
}

Remember to adjust the logging level and providers based on the environment (development, staging, production) to control the amount and type of log data generated.

21. Can you explain the difference between IApplicationBuilder, IHostingEnvironment, and ILogger? (Core Components)

IApplicationBuilder, IHostingEnvironment, and ILogger are core components in the .NET Core framework with distinct responsibilities:

• IApplicationBuilder: This interface is used to configure the HTTP request pipeline. Middleware components to handle requests and responses are registered using this interface. It’s used in the Configure method in the Startup class.

public void Configure(IApplicationBuilder app)
{
    app.UseMiddleware<SomeMiddleware>();
}

• IHostingEnvironment (renamed to IWebHostEnvironment in .NET Core 3.0 and later): This interface provides information about the web hosting environment an application is running in. It can be used to set up different configurations for different environments, like Development, Staging, or Production.

public void ConfigureServices(IServiceCollection services)
{
    if (_env.IsDevelopment())
    {
        // Development specific services
    }
    else
    {
        // Staging/Production services
    }
}

• ILogger: This interface is used for logging purposes. It supports structured logging, log levels, and integrates with multiple logging providers like console, debug, event source, and third-party loggers.

public class SomeService
{
    private readonly ILogger _logger;

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

    public void DoWork()
    {
        _logger.LogInformation("Work has started.");
    }
}

22. How do you handle session state in a .NET Core web application? (State Management)

In a .NET Core web application, you can handle session state using several approaches:

• Use the built-in session middleware: To enable session state, you need to add the session middleware to your ConfigureServices method and configure it, then add the session middleware to the request pipeline.

public void ConfigureServices(IServiceCollection services)
{
    services.AddDistributedMemoryCache();
    services.AddSession(options =>
    {
        options.IdleTimeout = TimeSpan.FromMinutes(30);
        options.Cookie.HttpOnly = true;
    });
}

public void Configure(IApplicationBuilder app)
{
    app.UseSession();
}

• Use distributed cache: For a more scalable solution, you can use a distributed cache like Redis or SQL Server to store session state.

• Use cookies: Cookies can also be used to store session data, but they are limited in size and are sent with every HTTP request.

• Use a custom solution: For complex scenarios, you might need to implement a custom state management solution.

23. Describe how you would implement a background service in .NET Core. (Background Processing)

Implementing a background service in .NET Core involves creating a class that inherits from BackgroundService and overriding the ExecuteAsync method:

public class MyBackgroundService : BackgroundService
{
    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
    {
        while (!stoppingToken.IsCancellationRequested)
        {
            // Your background task logic here
            await Task.Delay(TimeSpan.FromHours(1), stoppingToken);
        }
    }
}

You would then register this service in your Startup class:

public void ConfigureServices(IServiceCollection services)
{
    services.AddHostedService<MyBackgroundService>();
}

24. What is the .NET Core CLI and how do you use it? (Tooling)

The .NET Core Command Line Interface (CLI) is a cross-platform toolchain for developing, building, running, and publishing .NET Core applications. You use it through a series of commands in the terminal.

Examples of common .NET Core CLI commands include:

• dotnet new creates a new project, file, or solution.
• dotnet build builds a .NET Core project.
• dotnet run runs a .NET Core project.
• dotnet test runs tests using a test runner.
• dotnet publish publishes a .NET Core app for deployment.

25. How do you ensure that your .NET Core application is secure against common vulnerabilities? (Security)

Ensuring a .NET Core application is secure involves multiple practices:

• Authentication and Authorization: Use ASP.NET Core Identity or other identity providers to implement authentication and authorization.

• Data Protection: Use the data protection APIs to protect sensitive data.

• HTTPS: Enforce HTTPS to ensure all communication is encrypted.

• Secure Coding Practices: Follow secure coding practices such as validating input, encoding output, and handling errors properly.

• Use security headers and cookies properties: Set HTTP security headers and configure cookies with Secure, HttpOnly, and SameSite attributes.

• Dependency scanning: Regularly scan dependencies for known vulnerabilities.

• Logging and Monitoring: Implement robust logging and monitoring to detect and respond to security incidents.

• Regular Updates: Keep your .NET Core platform and libraries up to date with the latest security patches.

• Security Compliance Standards: Ensure compliance with security standards like OWASP, GDPR, and others as applicable.

Here is a markdown table summarizing security practices:

Security Practice	Description
Authentication & Authorization	Implement using ASP.NET Core Identity or other providers.
Data Protection	Utilize the data protection APIs for encryption and secure storage.
HTTPS	Redirect HTTP to HTTPS and enforce SSL/TLS encryption.
Secure Coding Practices	Validate input, encode output, and handle exceptions securely.
Security Headers & Cookies	Set HTTP security headers and configure secure cookie properties.
Dependency Scanning	Use tools to scan for vulnerabilities in project dependencies.
Logging & Monitoring	Track and monitor security-related events.
Regular Updates	Apply updates for .NET Core and dependencies.
Security Compliance	Align with standards like OWASP, GDPR, etc.

4. Tips for Preparation

To prepare for a .NET Core interview, begin by thoroughly reviewing the fundamental concepts of .NET Core, its architecture, and the differences from the .NET Framework. Brush up on the key features like dependency injection, middleware, and new APIs. Practice coding common scenarios and understand the functionality of essential classes and libraries.

Additionally, given the evolving nature of .NET Core, stay current with the latest updates and releases. Engage with the community, contribute to open-source projects, or build a personal project to demonstrate practical understanding. Soft skills can also be pivotal, so prepare to showcase problem-solving abilities, collaborative experiences, and scenarios where you’ve taken the lead.

5. During & After the Interview

During the interview, communicate clearly and confidently. Interviewers look for candidates who can articulate their thought process and reasoning. Be prepared to explain your code and design choices, as well as how you stay updated with the latest tech trends in .NET Core.

Avoid common pitfalls such as speaking negatively about past employers or projects. Instead, focus on what you learned from challenging situations. It’s also crucial to ask insightful questions about the company’s tech stack, development practices, or future projects, which shows your genuine interest.

Post-interview, send a thank-you email to express appreciation for the opportunity. This should be done within 24 hours of your interview. As for feedback, companies typically outline their timeline for getting back to you. If they don’t, it’s appropriate to ask at the end of the interview or to follow up after a week if you haven’t heard back.