New 50 .NET CORE Interview Questions

Introduction

.NET Core is a free, open-source, cross-platform framework for building modern applications, including web, desktop, mobile, gaming, IoT, and AI. It was developed by Microsoft and released in 2016 as a successor to the .NET Framework. .NET Core also comes with a rich set of libraries and tools that help developers build scalable, secure, and reliable applications. These include ASP.NET Core for building web applications, Entity Framework Core for database access, and Visual Studio Code for coding and debugging.

Basic Questions

1. What is .NET Core?

.NET Core is a free, open-source, cross-platform framework for building modern applications, including web, desktop, mobile, gaming, IoT, and AI. It was developed by Microsoft and released in 2016 as a successor to the .NET Framework.

2. What are the benefits of using .NET Core?

Some of the benefits of using .NET Core include cross-platform compatibility, high performance, a large community of developers, versatility, and integration with Microsoft technologies.

3. What is the difference between .NET Core and .NET Framework?

The main difference between .NET Core and .NET Framework is that .NET Core is cross-platform, while .NET Framework only runs on Windows. Additionally, .NET Core is open-source, while .NET Framework is not.

4. What is ASP.NET Core?

Answer: ASP.NET Core is a framework for building web applications using .NET Core. It provides a modular and flexible architecture that allows developers to build scalable and high-performance web applications.

5. What is Entity Framework Core?

Answer: Entity Framework Core is an Object-Relational Mapping (ORM) framework for .NET Core. It allows developers to work with databases using objects and provides a simplified approach to database programming.

6. What is the use of webHostBuilder()?

The webHostBuilder() method is used to create and configure an instance of the ASP.NET Core web host, which is responsible for running and managing the application’s web server. It allows developers to customize and configure the web host to suit their application’s requirements, such as setting up HTTP/HTTPS endpoints, configuring middleware, setting up logging, and much more.

7. What is middleware in ASP.NET Core?

Answer: Middleware in ASP.NET Core is a set of components that handle requests and responses in the application pipeline. It provides a way to add cross-cutting concerns, such as authentication and logging, to the application.

8. What is dependency injection in .NET Core?

Answer: Dependency injection in .NET Core is a design pattern that allows objects to receive their dependencies from an external source rather than creating them themselves. It promotes decoupling and testability by making it easy to swap out dependencies during testing.

9. What is a NuGet package in .NET Core?

Answer: A NuGet package in .NET Core is a collection of files that can be used to add functionality or libraries to a project. It is a standard format for distributing code and dependencies in the .NET ecosystem.

10. What is CoreFx?

CoreFX is a set of libraries, runtime components, and tools that provide the foundational building blocks for .NET Core. It is an open-source project developed by Microsoft and hosted on GitHub. CoreFX provides a common set of APIs for .NET Core across different platforms, including Windows, Linux, and macOS.

CoreFX includes a wide range of libraries and runtime components, including the following:

• Base Class Library (BCL)
• Networking
• Cryptography
• Threading
• File System
• Console
• Collections
• XML
• JSON
• and many more

Developers can use these libraries and components to build cross-platform applications and services in .NET Core. CoreFX is designed to be modular and extensible, allowing developers to pick and choose the components they need for their specific application requirements.

11. Explain the usage of SQL Scripts in .NET Core.

SQL scripts can be used in .NET Core to create and modify a database schema, tables, stored procedures, and other database objects. They are typically written in SQL (Structured Query Language), a programming language used for managing relational databases. To execute SQL scripts in .NET Core, you can use a variety of tools and frameworks, such as Entity Framework Core, Dapper, or raw ADO.NET. These tools allow you to connect to a database, execute SQL commands, and retrieve data from the database.

12. What is the role of the dotnet CLI in .NET Core?

Answer: The dotnet CLI (Command Line Interface) in .NET Core is a tool for creating, building, and deploying applications from the command line. It provides a streamlined workflow for developers and allows them to work with .NET Core applications without using a graphical user interface.

13. What is the difference between a .NET Core console application and a .NET Core web application?

Answer: A .NET Core console application is a type of application that runs in a command prompt or terminal window and typically performs a specific task or operation. A .NET Core web application, on the other hand, is a type of application that runs on a web server and serves content over the internet. It can be accessed using a web browser and typically provides a user interface for interacting with the application.

14. What is Razor syntax in ASP.NET Core?

Answer: Razor syntax in ASP.NET Core is a markup syntax that enables the creation of dynamic web pages with server-side code. It allows developers to embed C# code directly into HTML markup and simplifies the process of creating dynamic content.

15. What is the difference between .NET Core and .NET 5?

Answer: .NET 5 is a new version of the .NET platform that includes both .NET Core and .NET Framework components. It is designed to provide a unified platform for building modern applications on Windows, macOS, and Linux.

16. What is the difference between an interface and an abstract class in .NET Core?

Answer: An interface in .NET Core defines a contract that a class must implement, while an abstract class provides a partial implementation that

17. Which languages can we use with .NET CORE?

.NET Core is designed to support multiple programming languages. The following languages are supported by .NET Core:

1. C#
2. Visual Basic (VB.NET)
3. F#
4. C++/CLI (Managed C++)
5. IronPython
6. IronRuby
7. PHP (via Peachpie)
8. Rust (via Project Tye)

Additionally, .NET Core can be used with other languages via language interop, which allows code written in one language to be used by code written in another language. For example, a C# library can be used by a Python application via language interoperability.

Intermediate Questions

18. What is the difference between synchronous and asynchronous programming in .NET Core?

Synchronous programming blocks the execution of code until a task is completed, while asynchronous programming allows multiple tasks to be executed concurrently without blocking the main thread.

19. What is the purpose of the appsettings.json file in .NET Core?

The appsettings.json file is used to store application settings and configuration data in a structured format that can be easily accessed and modified.

20. What is the difference between a library and a framework in .NET Core?

A library in .NET Core is a collection of reusable code that can be referenced by other projects. A framework, on the other hand, provides a set of guidelines and tools for building applications.

21. What is a delegate in .NET Core?

A delegate in .NET Core is a type that represents a reference to a method with a particular signature. It provides a way to encapsulate a method and pass it as a parameter or return value to other methods, allowing for more flexible and modular code. Delegates are often used in event handling, as well as in LINQ queries and other functional programming constructs.

22. What is Kestrel?

Kestrel is a high-performance web server that hosts .NET applications, designed to be lightweight and fast. It is event-driven and I/O-based, making it highly scalable and efficient. Being an open-source and cross-platform server, it is compatible with all platforms that support .NET Core.

Kestrel is primarily used as an edge server, serving as a direct interface between the internet and web clients, and is operated via a command-line interface. One of its key advantages is its support for HTTPS, ensuring secure communication between clients and the server.

Kestrel is also easy to configure, making it a popular choice for hosting modern web applications. With its high scalability, fast performance, and versatile configuration options, Kestrel is a powerful and flexible server for hosting .NET Core applications.

23. What differences can you state between .NET CORE and MONO?

Here is a table outlining some of the key differences between .NET Core and Mono:

These are just some of the key differences between .NET Core and Mono. Both frameworks have their own strengths and weaknesses, and the choice of which to use will depend on your specific needs and requirements.

24. What is the difference between IQueryable and IEnumerable in .NET Core?

When working with data in .NET Core, it’s important to understand the differences between IQueryable and IEnumerable interfaces. While both interfaces are used for querying data, they have distinct purposes and behaviors. The main advantage of IQueryable is its support for deferred execution, which allows for more complex querying and filtering to be performed at the database level, making it more suitable for larger datasets or remote data sources. In contrast, IEnumerable is better suited for in-memory collection operations on smaller datasets. By understanding the differences between these two interfaces, you can optimize your code for performance and scalability.

25. What do you understand by UWP Applications in .NET CORE?

Universal Windows Platform (UWP) apps in .NET Core are a type of application that can run on a variety of devices that support Windows 10. UWP is a platform-specific framework that provides a set of APIs and programming models for building apps that can run across all Windows 10 devices, including desktops, laptops, tablets, smartphones, Xbox consoles, and HoloLens devices.

UWP apps in .NET Core are built using the .NET Core runtime and .NET Standard libraries, which are designed to provide a unified programming model for developing applications that can run on different platforms. UWP apps can be developed using a variety of programming languages, including C#, C++, and JavaScript, and can be deployed through the Microsoft Store or other distribution channels.

Some of the key features of UWP apps in .NET Core include:

• Support for a wide range of Windows 10 devices, including mobile, desktop, and IoT devices.
• Ability to use Windows 10 platform features, such as Cortana, Live Tiles, and in-app purchases.
• A sandboxed environment for running apps that provides security and protection from malicious code.
• Support for modern UI design principles, such as adaptive layout, touch input, and high DPI scaling.
• Integration with the Windows Store for distribution and monetization of apps.

26. What is the role of the DbContext class in Entity Framework Core?

Here are some key points regarding the role of the DbContext class in Entity Framework Core:

• The DbContext class represents a session with the database.
• It provides a way to query, insert, update, and delete data in the database.
• It contains a DbSet property for each entity in the database.
• A DbSet is a collection of objects that represent the data in a table or view.
• You can query the data in a DbSet using LINQ syntax.
• The DbContext class can be used to configure the database connection and specify database provider-specific options.
• It can be used to define relationships between entities.
• It provides functionality for creating database migrations and managing database schema.
• The DbContext class provides an object-relational mapping (ORM) layer between the application code and the underlying database, making it easier to work with data in the database from the application.

27. What is the role of the HostBuilder class in .NET Core?

The HostBuilder class is a key component of the .NET Core application hosting model. It is responsible for configuring and building the host environment, which provides services and configuration information that the application needs to run.

The HostBuilder is used to create an instance of the generic Host class, which is responsible for managing the application’s lifetime and running its components. The HostBuilder provides a fluent API for configuring the host environment, including setting up logging, configuring dependency injection, and adding configuration sources.

28. Explain the difference between .NET CORE SDK and .NET CORE Runtime.

The .NET Core SDK and .NET Core Runtime are two different components of the .NET Core platform with distinct purposes.

The .NET Core SDK (Software Development Kit) includes everything required to develop and build .NET Core applications. It includes the .NET Core Runtime, as well as tools for developing and testing .NET Core applications, such as the command-line interface (CLI) tools, debugging tools, and compilers. The SDK is typically used by developers who are creating and building .NET Core applications.

The .NET Core Runtime, on the other hand, is a subset of the SDK that includes only the components required to run .NET Core applications. It includes the .NET Core libraries and runtime environment but does not include the tools required for development, such as compilers and debugging tools. The Runtime is typically used by end-users who want to run .NET Core applications on their machine.

In summary, the .NET Core SDK is used by developers to build, test, and debug .NET Core applications, while the .NET Core Runtime is used by end-users to run .NET Core applications.

29. What is the difference between a factory method and a constructor in .NET Core?

The key difference between a constructor and a factory method is that a constructor is part of the class definition and is responsible for initializing the object, while a factory method is a separate method that creates and returns instances of the class. A factory method can also provide additional functionality, such as caching or object pooling, that is not possible with a constructor.

30. What is the difference between a static class and a non-static class in .NET Core?

In .NET Core, a static class is a class that can only contain static members, such as static fields, static methods, and static properties. It cannot be instantiated, meaning that you cannot create objects from it using the “new” keyword. Instead, you access its members using the class name itself, without needing to create an instance of the class.

A non-static class, on the other hand, can contain both static and non-static members. It can be instantiated, meaning that you can create objects from it using the “new” keyword, and each instance of the class has its own set of instance variables and methods. You can access its static members using the class name, but you need to create an instance of the class to access its instance members.

31. What is the difference between dependency injection and inversion of control in .NET Core?

Inversion of control is a design principle that advocates for delegating control of object creation and management to a separate component, known as the IoC container. The IoC container is responsible for managing the lifecycle of objects and providing them to other components when requested. This helps to decouple components and makes the application more flexible and extensible.

Dependency injection, on the other hand, is a technique for implementing IoC. It involves passing dependencies into a component from an external source, such as the IoC container, rather than having the component create or manage its dependencies itself. This allows the component to be more modular and easier to test, as dependencies can be easily replaced with mock objects.

Advanced Questions

32. What is Dependency Injection in .NET CORE and why is it useful?

Dependency Injection (DI) is a design pattern used in .NET Core to provide a way to create and manage objects with their dependencies. It’s a technique that allows the separation of the creation of objects from their usage, thus reducing coupling and making the code more testable, maintainable, and flexible.

In DI, the dependencies required by a class are passed to it through its constructor, property, or method. These dependencies can be other objects, services, or resources that the class needs to perform its functions. The .NET Core framework provides built-in support for dependency injection through Microsoft.Extensions.DependencyInjection package. It allows developers to define services and configure the DI container to inject them into the classes that require them.

There are several advantages to using DI in .NET Core, including:

1. Reduced coupling: DI helps to reduce the coupling between components by removing the hard-coded dependencies from the code.
2. Testability: DI makes the code more testable by allowing easily mocked or stubbed dependencies.
3. Maintainability: DI makes the code more maintainable by making it easier to add or remove dependencies.
4. Flexibility: DI allows for more flexibility in the code by allowing the same component to be used in different contexts with different dependencies.

33. How does .NET Core handle multi-threading and concurrency, and what are some best practices for writing thread-safe code in .NET Core?

.NET Core provides several mechanisms for handling multi-threading and concurrency, including the Task Parallel Library (TPL), which provides a set of classes and methods for running tasks asynchronously and in parallel, and the Concurrent Collections, which are thread-safe data structures that can be used to safely share data between threads.

To write thread-safe code in .NET Core, some best practices include:

1. Use locking: Use the lock keyword to ensure that only one thread at a time can access a shared resource. This prevents race conditions and other synchronization issues.
2. Use thread-safe data structures: Use the Concurrent Collections provided by .NET Core to safely share data between threads. These data structures are designed to handle concurrent access and modification.
3. Avoid shared state: Whenever possible, avoid sharing state between threads. Instead, try to design your application so that each thread has its own state.
4. Use immutability: Use immutable objects whenever possible. Immutable objects are inherently thread-safe since they cannot be modified once created.
5. Use async/await: Use the async/await keywords to write asynchronous code. This allows your application to continue processing other requests while waiting for long-running operations to complete.

34. How does .NET Core handle garbage collection, and what are some best practices for managing memory in .NET Core applications?

Garbage collection (GC) is a mechanism used by .NET Core to automatically manage memory in applications. It periodically identifies and frees the memory that is no longer being used by the application, thereby preventing memory leaks and improving application performance. 

The .NET Core runtime includes a garbage collector that runs on a separate thread and manages the memory for all the managed code running in the process.In .NET Core, the garbage collector uses a generational model, where objects are divided into three generations based on their age. The youngest generation is garbage collected more frequently than the older generations.

To manage memory effectively in .NET Core applications, some best practices include:

1. Avoiding unnecessary object creation: Create objects only when they are needed, and reuse them when possible. This reduces the amount of memory allocated and the frequency of garbage collection.
2. Using value types when appropriate: Use value types, such as integers and booleans, instead of reference types when appropriate. Value types are allocated on the stack, which is faster than allocating memory on the heap.
3. Limiting the scope of objects: Limit the scope of objects to the smallest possible scope. This reduces the time that an object is in memory and improves garbage collection performance.
4. Using disposable objects: Use objects that implement the IDisposable interface, such as database connections and file streams, and dispose of them when they are no longer needed. This ensures that resources are released promptly and reduces the amount of memory used by the application.
5. Using performance profiling tools: Use performance profiling tools, such as dotMemory and ANTS Memory Profiler, to identify memory leaks and other memory-related issues in the application.

35. Are debugging and tracing the same in .NET CORE?

Debug and Trace are two different mechanisms used for logging in to .NET Core, although they share some similarities.

Debug is used for diagnostic logging during development and testing. It provides a simple way to write debug messages to the console or log files, and it is typically used to help developers debug and diagnose issues during development. Debug messages are typically not included in production code, as they can impact performance and generate unnecessary log data.

Trace, on the other hand, is used for application-level logging in both development and production. It provides a more fine-grained way to log messages at various levels of severity, such as informational messages, warnings, and errors. Trace messages are typically written to log files, and they can be used to monitor the health and performance of an application in production.

In summary, Debug is primarily used for diagnostic logging during development, while Trace is used for application-level logging in both development and production. While they share some similarities, they serve different purposes and are used in different contexts.

36. What are the differences between .NET Core and .NET Framework, and when should you choose one over the other for your application?

.NET Core and .NET Framework are both software development frameworks used to build Windows applications. However, they have several key differences:

1. Cross-platform compatibility: .NET Core is designed to be cross-platform and can be used to build applications for Windows, Linux, and macOS, while .NET Framework is only available for Windows.
2. Size and modularity: .NET Core is smaller and more modular than .NET Framework. It includes only the libraries needed for an application, whereas .NET Framework includes a large number of libraries that may not be necessary for an application.
3. Deployment: .NET Core can be deployed as a single self-contained executable, while .NET Framework requires the framework to be installed on the target machine.
4. API compatibility: .NET Core has a smaller API surface area than .NET Framework, which means that some libraries and features that are available in .NET Framework may not be available in .NET Core.
5. Performance: .NET Core is generally faster and more performant than .NET Framework, especially in web applications.

When choosing between .NET Core and .NET Framework for an application, several factors should be considered. If cross-platform compatibility is a requirement, .NET Core would be the better choice. If the application is Windows-only and requires access to a large number of libraries, .NET Framework may be a better option. 

In general, if you are building a new application, .NET Core is the recommended choice due to its smaller size, better performance, and cross-platform compatibility. However, if you are maintaining an existing application that was built on .NET Framework, it may be more practical to continue using .NET Framework.

37. How can you optimize the performance of a .NET Core application, and what tools are available for profiling and diagnosing performance issues?

Optimizing the performance of a .NET Core application can be critical for ensuring it runs efficiently and meets its performance requirements. Here are some strategies and tools that can help improve the performance of a .NET Core application:

1. Use async/await: Asynchronous programming can improve the performance of applications that make network or I/O bound calls. The use of async/await can help avoid blocking the main thread of the application, which can lead to a more responsive and efficient application.
2. Avoid excessive memory allocation: Excessive memory allocation can slow down an application’s performance by increasing the frequency of garbage collection. To optimize memory allocation, consider reusing objects where possible, using value types, and using struct types instead of class types.
3. Optimize database queries: Inefficient database queries can significantly impact an application’s performance. Ensure that queries are optimized and use appropriate indexing.
4. Use caching: Caching frequently accessed data can improve the performance of an application by reducing the need to repeatedly retrieve the same data from a database or external service.
5. Use a profiler: Profilers are tools that can help diagnose performance issues in an application by identifying hot spots in the code that are consuming the most resources. Some popular profiling tools for .NET Core include JetBrains dotTrace, Visual Studio Profiler, and PerfView.
6. Use a load testing tool: Load testing tools, such as Apache JMeter and LoadRunner, can help simulate a high volume of traffic to an application to identify performance bottlenecks and ensure that the application can handle the expected load.
7. Use a monitoring tool: Monitoring tools, such as Application Insights and New Relic, can provide real-time insights into an application’s performance by monitoring metrics such as CPU usage, memory usage, and request throughput.

By implementing these strategies and using these tools, developers can identify and address performance issues in their .NET Core applications, leading to a more efficient and responsive application.

38. What are the security features provided by .NET Core?

.NET Core provides several security features and best practices for securing applications. Here are some of the security features provided by .NET Core and some best practices for securing a .NET Core application:

1. Authentication and Authorization: .NET Core includes built-in support for authentication and authorization, allowing developers to easily authenticate users and control access to resources based on user roles and permissions.
2. Data Protection: .NET Core includes the Data Protection API, which provides a set of cryptographic APIs for encrypting and decrypting sensitive data such as passwords and session data.
3. Cross-site Scripting (XSS) and Cross-site Request Forgery (CSRF) protection: .NET Core provides built-in protection against XSS and CSRF attacks, which can help prevent attacks that exploit web application vulnerabilities.
4. Input Validation: Input validation is a key component of web application security, and .NET Core includes built-in validation attributes that can help prevent attacks that exploit input vulnerabilities such as SQL injection and command injection.
5. Security headers: .NET Core supports adding security headers to HTTP responses, which can help protect against various attacks such as cross-site scripting (XSS) and clickjacking.

39. What are some best practices for securing a .NET Core application?

In addition to these security features, here are some best practices for securing a .NET Core application:

1. Use HTTPS: HTTPS encrypts all data sent between the client and the server, providing protection against eavesdropping and tampering.
2. Keep software up-to-date: Ensure that the .NET Core runtime and all third-party libraries used by the application are up-to-date with the latest security patches and updates.
3. Avoid storing sensitive data in plain text: Sensitive data such as passwords and keys should be encrypted and stored securely, using the Data Protection API or a third-party encryption library.
4. Use strong passwords and authentication mechanisms: Enforce strong passwords and authentication mechanisms to prevent unauthorized access to the application.
5. Use least privilege: Limit access to resources and functionality to only those users who need it, and give users the lowest level of access required to perform their tasks.

By implementing these security features and best practices, developers can help ensure that their .NET Core applications are secure and protected against common security vulnerabilities and attacks.

40. How can you integrate a .NET Core application with other technologies and platforms, such as Docker, Kubernetes, and Azure? What are some best practices for deploying and managing .NET Core applications in these environments?

Integrating a .NET Core application with other technologies and platforms can provide a range of benefits such as improved scalability, portability, and maintainability. Here are some ways to integrate a .NET Core application with other technologies and platforms, and some best practices for deploying and managing .NET Core applications in these environments:

1. Docker: Docker is a containerization platform that enables developers to package an application and all its dependencies into a single container, which can then be deployed to any environment that supports Docker. To integrate a .NET Core application with Docker, developers can create a Dockerfile that specifies the application’s dependencies, and then use the Docker CLI to build and deploy the container to a Docker registry or a Kubernetes cluster. Some best practices for deploying a .NET Core application in Docker include minimizing the size of the container, using multi-stage builds to reduce the attack surface, and using a service registry and load balancer to manage multiple containers.

2. Kubernetes: Kubernetes is a container orchestration platform that enables developers to deploy and manage containers at scale. To integrate a .NET Core application with Kubernetes, developers can create a Kubernetes deployment manifest that describes the application’s requirements, and then use the Kubernetes CLI to deploy the application to a Kubernetes cluster. Some best practices for deploying a .NET Core application in Kubernetes include using Kubernetes secrets to store sensitive configuration data, using liveness and readiness probes to monitor the health of the application, and using horizontal pod autoscaling to automatically scale the application based on resource usage.

3. Azure: Azure is a cloud computing platform that provides a range of services for deploying, managing, and scaling applications. To integrate a .NET Core application with Azure, developers can use Azure DevOps to automate the build and deployment process and use Azure App Service to deploy the application to a cloud environment. Some best practices for deploying a .NET Core application in Azure include using Azure Application Insights to monitor the application’s performance and usage, using Azure Key Vault to store sensitive configuration data, and using Azure Load Balancer and Azure Traffic Manager to manage traffic and distribute the load.

41. Explain MVC in .NET CORE and state its advantages.

MVC (Model-View-Controller) is a design pattern that is commonly used to build web applications. It separates the application logic into three interconnected components: Model, View, and Controller.

In .NET Core, MVC is a framework that provides a standard way to build web applications using the MVC pattern. Here is a brief explanation of each component:

1. Model: The Model represents the data and the business logic of the application. It can be any object or data structure that the application needs to manipulate or store.
2. View: The View is responsible for presenting the Model data to the user in a human-readable format. It can be an HTML page, a JSON response, or any other format that can be displayed in a web browser.
3. Controller: The Controller acts as a mediator between the Model and the View. It receives requests from the user and decides how to handle them. It interacts with the Model to retrieve or update data and then passes the data to the View for display.

In the context of .NET Core MVC, the framework provides a set of abstractions and APIs that simplify the implementation of the MVC pattern. For example, the framework provides a base Controller class that developers can extend to define their own Controllers and a set of built-in View templates that developers can use to create Views.

The following are some of the advantages of using the MVC pattern in .NET Core:

1. Separation of concerns: The MVC pattern separates the application into three components, each with its own responsibility. This makes it easier to maintain and scale the application.
2. Testability: Because the components are separated, it’s easier to test each component in isolation, which makes testing the application more efficient and effective.
3. Reusability: The components can be reused in different parts of the application or in different applications altogether, which reduces development time and costs.
4. Flexibility: MVC provides the flexibility to swap out one component for another without affecting the rest of the application. For example, you could replace the view with a different one without having to change the model or controller.
5. Improved performance: MVC is a lightweight framework that can improve application performance, especially in high-traffic scenarios.

42. Explain .NET CORE CLI and give some examples.

.NET Core CLI (Command Line Interface) is a set of command-line tools that allow developers to create, build, and manage .NET Core applications without relying on an integrated development environment (IDE) such as Visual Studio.

The .NET Core CLI is a powerful tool that allows developers to work with .NET Core applications from the command line, which can be especially useful for automation and continuous integration scenarios. It also provides a lightweight alternative to a full-featured IDE for developers who prefer to work with text editors or prefer a more streamlined development environment.

Here are some examples of how you can use .NET Core CLI to perform common tasks:

1. Creating a new project: You can use the following command to create a new .NET Core project from a template:

   dotnet new <template> -o <output directory>

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

   dotnet new webapp -o MyWebApp

2. Building a project: Once you have created a new project, you can use the following command to build it:

   dotnet build

This command compiles the source code and creates a binary executable or library.

3. Running a project: You can use the following command to run a .NET Core application:

   dotnet run

This command launches the application in a development server.

4. Managing dependencies: You can use the following command to restore dependencies for a project:

dotnet restore

This command downloads and installs the dependencies specified in the project’s configuration file.

5. Publishing an application: You can use the following command to publish a .NET Core application for deployment:

dotnet publish -c Release -o <output directory>

This command creates a self-contained package of the application that can be deployed to   a production environment.

6. Running tests: You can use the following command to run unit tests for a project:

  dotnet test

This command discovers and runs tests in the project.

43. What is CTS in .NET CORE, explain its types.

CTS stands for Common Type System, which is a fundamental component of the .NET Framework and .NET Core. The CTS defines a set of rules and guidelines that all .NET languages must follow in order to ensure that objects created in one language can be accessed and manipulated by other .NET languages. In other words, the CTS defines a common type system that is shared by all .NET languages.

The CTS includes the following types:

1. Value Types: Value types are types that store their values directly, rather than through a reference. They include primitive types such as integers, floating-point numbers, and Booleans, as well as user-defined structs.
2. Reference Types: Reference types are types that store a reference to the location in memory where the object’s data is stored. They include classes, arrays, strings, and delegates.
3. Pointer Types: Pointer types allow direct manipulation of memory addresses, and are used primarily in unsafe code.
4. Object Types: Object types are the base type for all types in .NET, and include all classes, arrays, strings, and delegates.
5. Interface Types: Interface types define a contract that a class must implement in order to be considered compatible with the interface. They are used extensively in .NET Core to enable polymorphism and code reuse.

The CTS is important because it allows developers to write code in multiple languages that can interact with each other seamlessly. By defining a common set of types and rules for how those types can be used, the CTS enables interoperability between languages and makes it easier to reuse code across different projects and platforms.

44. What do you understand by State Management?

State management is an important aspect of building modern web applications, and .NET Core provides several options for managing the state in web applications.

1. Session state: Session state allows you to store and retrieve user-specific data on the server side across multiple requests. In .NET Core, the session state is managed using the ‘ISession‘ interface, and you can store and retrieve data using key-value pairs.
2. Cache: Cache allows you to store frequently used data in memory so that it can be quickly retrieved when needed. In .NET Core, caching can be performed using the ‘IMemoryCache' interface, which provides methods for storing and retrieving data from memory.
3. TempData: TempData is a feature in .NET Core that allows you to store data between two consecutive requests. It is typically used to store data that needs to be displayed to the user after a redirect.
4. Stateful services: Stateful services allow you to store and manage the state within a service. In .NET Core, stateful services can be created using the ‘IStatefulService‘ interface, which provides methods for managing the state within a service.
5. Distributed cache: Distributed cache allows you to store frequently used data in a distributed cache, such as Redis or Azure Cache for Redis. In .NET Core, the distributed cache can be performed using the ‘IDistributedCache‘ interface, which provides methods for storing and retrieving data from a distributed cache.

45. Explain CoreRT and state some of its characteristics.

CoreRT is a runtime for .NET Core that is optimized for use in native code applications. Unlike the standard .NET Core runtime, which relies on just-in-time (JIT) compilation, CoreRT uses ahead-of-time (AOT) compilation to generate native code that can be executed directly by the operating system. This results in faster startup times, smaller memory footprints, and better performance for certain types of applications. CoreRT is primarily used for building high-performance serverless functions, IoT applications, and other performance-critical scenarios.

Here are some key characteristics of CoreRT:

1. AOT Compilation: CoreRT uses AOT compilation to generate native code that can be executed directly by the operating system. This results in faster startup times, smaller memory footprint, and better performance for certain types of applications.
2. Cross-Platform: CoreRT is cross-platform and can run on a variety of operating systems, including Windows, Linux, and macOS.
3. Lightweight: CoreRT is designed to be lightweight and can be used to build high-performance serverless functions, IoT applications, and other performance-critical scenarios.
4. Subset of .NET Core: CoreRT is a subset of the .NET Core platform, and includes only the essential features needed to run .NET Core applications.
5. Open-Source: CoreRT is an open-source project and is available on GitHub.
6. Used for Native Code Applications: CoreRT is primarily used for building native code applications, where performance is critical and AOT compilation is preferred over JIT compilation.

46. What is MEF in .NET CORE? State some of its advantages.

MEF (Managed Extensibility Framework) is a framework used in .NET Core for composing and managing extensible applications. It provides a way for developers to write modular applications, where the functionality is divided into smaller components called modules or plugins. MEF allows developers to easily discover and load modules at runtime, which makes the application more flexible and extensible.

The main advantages of using MEF in .NET Core are:

1. Easy extensibility: MEF allows for dynamic loading of components at runtime, which makes it easier to add new features or update existing ones without disrupting the rest of the application.
2. Loose coupling: MEF allows for loose coupling between components. Components can be added or removed without affecting the rest of the application, making it easier to maintain and test the application.
3. Easy discovery: MEF provides a way for components to discover and load other components at runtime, which makes it easier to create extensible applications.
4. Easy configuration: MEF provides a way to configure the application using metadata. This makes it easier to change the behavior of the application without changing the code.
5. Integration with .NET Core: MEF is integrated with the .NET Core framework, which makes it easy to use in .NET Core applications.

Overall, MEF is a powerful and flexible framework that can be used to create modular and extensible applications in .NET Core. It is a useful tool for developers who want to create applications that can evolve and adapt over time.

47. What is JIT in .NET CORE? What are the different types of JIT?

JIT (Just-In-Time) is a mechanism used by the .NET runtime to convert compiled code (MSIL) into native code that can be executed by the CPU. JIT allows for faster execution of the code by optimizing it for the specific hardware platform it’s running on. There are two types of JIT compilers in .NET:

1. Pre-JIT: In Pre-JIT, the entire application is compiled to native code at once, before it is executed. This can take some time, but it provides fast startup time since the code is already compiled. However, this approach is not flexible since it requires recompilation of the entire application every time it changes.

2. Just-In-Time (JIT): In JIT, the compiled code is converted to native code on-the-fly, as the code is executed. This allows for more flexibility since only the code that is actually executed needs to be compiled. JIT compilation can be further divided into two types:

1. Normal JIT: In Normal JIT, only the code that is called at runtime is compiled to native code, which reduces the startup time of the application. However, this can result in some performance overhead since the code is compiled each time it is called.
2. Econo-JIT: Econo-JIT is a more efficient version of Normal JIT. In this type of JIT, the compiled code is cached and reused each time it is called, which reduces the performance overhead of compilation. Econo-JIT is used in scenarios where the same code is executed repeatedly.

Overall, JIT is an important part of the .NET runtime, as it allows for fast and efficient execution of code, while also providing flexibility and adaptability.

48. Explain Generic Host and state some of its advantages.

The Generic Host in .NET Core is a hosting solution for building console-based applications, such as background services or worker processes. It is a lightweight and extensible hosting solution that provides a set of features and services to manage the lifecycle of an application.

The Generic Host is built on top of the .NET Core Dependency Injection (DI) framework, which allows you to easily configure and inject services into your application. It provides a common host builder API for configuring common services, such as logging, configuration, and dependency injection, as well as custom services that are specific to your application.

Some advantages of using the Generic Host include:

1. Easy configuration and extension: The Generic Host provides a common host builder API for configuring common services, such as logging, configuration, and dependency injection, as well as custom services that are specific to your application. This makes it easy to configure and extend your application without having to write a lot of boilerplate code.
2. Dependency injection: The Generic Host is built on top of the .NET Core Dependency Injection (DI) framework, which allows you to easily configure and inject services into your application. This makes it easy to decouple your application logic from its dependencies, making it easier to test and maintain.
3. Lifecycle management: The Generic Host provides a set of lifecycle events that allow you to hook into the startup and shutdown of your application, as well as a cancellation mechanism that allows you to gracefully shut down your application in response to external signals. This makes it easy to manage the lifecycle of your application and ensure that it starts up and shuts down cleanly.
4. Built-in logging: The Generic Host provides built-in support for logging, allowing you to easily log messages to the console, a log file, or a remote logging service. This makes it easy to monitor the health and performance of your application.
5. Cross-platform support: The Generic Host is built on top of .NET Core, which provides cross-platform support for building console-based applications. This makes it easy to build and deploy your application to a variety of platforms, including Windows, Linux, and macOS.

49. What is Explicit Compilation (Ahead of Time Compilation)?

Explicit Compilation, also known as Ahead-Of-Time (AOT) compilation, is a technique used in .NET Core to compile the application code into native machine code before the application is deployed. This process is done ahead of time, hence the name AOT.

When the application is deployed, the native code is executed directly by the operating system, without the need for a Just-In-Time (JIT) compilation step. This results in faster startup times, reduced memory usage, and improved performance.

In AOT compilation, the compiler generates a native binary executable that can be run directly on the target platform, without requiring the .NET runtime to be installed. This makes it easier to deploy .NET Core applications on platforms that don’t have a .NET runtime installed, such as some IoT devices, embedded systems, or legacy systems.

The explicit compilation is supported in .NET Core through the .NET Native toolchain, which is included in the .NET Core SDK. However, AOT compilation may not be suitable for all scenarios and should be used with caution. Some features of .NET Core, such as dynamic code generation or reflection, may not be fully supported in AOT-compiled applications.

50. Differentiate between ASP.NET and .NET CORE.

Here is a tabular comparison of ASP.NET Core and .NET Core:

Note that while ASP.NET Core is built on top of .NET Core, it provides additional functionality specific to web application development. On the other hand, .NET Core is a general-purpose development platform that can be used to build various types of applications, including web applications using ASP.NET Core.

MCQ Questions

51. Which of the following is a cross-platform, open-source, and modular framework for building modern web applications in .NET Core?
a. ASP.NET MVC
b. Entity Framework Core
c. Blazor
d. SignalR

Answer: c. Blazor

52. Which of the following is a lightweight and fast Object-Relational Mapping (ORM) tool for .NET Core?
a. Entity Framework Core
b. Dapper
c. NHibernate
d. Fluent NHibernate

Answer: b. Dapper

53. Which of the following is used for dependency injection in .NET Core?
a. Unity
b. Autofac
c. Castle Windsor
d. All of the above

Answer: d. All of the above

54. Which of the following is a cross-platform unit testing framework for .NET Core?
a. NUnit
b. MSTest
c. xUnit.net
d. All of the above

Answer: d. All of the above

55. Which of the following is a tool for automating the build process in .NET Core?
a. MSBuild
b. Gradle
c. Jenkins
d. Bamboo

Answer: a. MSBuild

56. Which of the following is a containerization platform used for deploying and managing .NET Core applications?
a. Docker
b. Kubernetes
c. OpenShift
d. All of the above

Answer: d. All of the above

57. Which of the following is a NuGet package manager for .NET Core?
a. dotnet pack
b. dotnet publish
c. dotnet restore
d. dotnet run

Answer: c. dotnet restore

58. Which of the following is a middleware component used for logging in .NET Core?
a. UseCors
b. UseHttpsRedirection
c. UseRouting
d. UseLogging

Answer: d. UseLogging

59. Which of the following is a data access technology used for querying and manipulating data in .NET Core?
a. LINQ
b. ADO.NET
c. Entity Framework Core
d. All of the above

Answer: d. All of the above

60. Which of the following is used for configuring the HTTP request pipeline in .NET Core?
a. Startup.cs
b. Program.cs
c. appsettings.json
d. All of the above

Answer: a. Startup.cs

61. Which of the following is a protocol used for real-time web functionality in .NET Core?
a. WebSocket
b. SignalR
c. REST
d. SOAP

Answer: b. SignalR

62. Which of the following is a package management tool used for .NET Core?
a. NuGet
b. Chocolatey
c. Homebrew
d. All of the above

Answer: a. NuGet

63. Which of the following is a template engine used for generating dynamic web pages in .NET Core?
a. Razor
b. Handlebars
c. Mustache
d. All of the above

Answer: a. Razor

64. Which of the following is a data access library used for accessing NoSQL databases in .NET Core?
a. Redis
b. MongoDB
c. Couchbase
d. All of the above

Answer: d. All of the above

65. Which of the following is used for configuring authentication and authorization in .NET Core?
a. UseAuthorization
b. UseAuthentication
c. UseCors
d. UseAuth

Answer: a. UseAuthentication

66. Which of the following is a cross-platform runtime for .NET Core?
a. NET Framework
b. Mono
c. Xamarin
d. Silverlight

Answer: b. Mono

67. Which of the following is a lightweight and fast web server used by .NET Core applications?
a. IIS
b. Apache
c. Kestrel
d. Tomcat

Answer: c. Kestrel

68. Which of the following is a CLI tool used to create, build, and manage .NET Core projects?
a. Visual Studio
b. MSBuild
c. NuGet
d. dotnet

Answer: d. dotnet

69. Which of the following is an ORM (Object-Relational Mapping) tool used in .NET Core to access databases?
a. Dapper
b. Entity Framework Core
c. NHibernate
d. All of the above

Answer: d) All of the above

70. Which of the following is a feature in .NET Core that allows developers to write code that can run on multiple operating systems?
a) Cross-platform compatibility
b) Multi-language support
c) JIT compilation
d) Garbage collection

Answer: a) Cross-platform compatibility

71. Which of the following is a class in .NET Core that is used to read configuration data from various sources?
a) IConfiguration
b) IConfigurationBuilder
c) IConfigurationProvider
d) None of the above

Answer: b) IConfigurationBuilder

72. Which of the following is a middleware component in .NET Core that is used to authenticate users?
a) AuthenticationMiddleware
b) AuthorizationMiddleware
c) CookieAuthenticationMiddleware
d) JwtBearerMiddleware

Answer: c) CookieAuthenticationMiddleware

73. Which of the following is a data access technology in .NET Core that allows developers to write SQL queries in C# code?
a) Dapper
b) LINQ to SQL
c) ADO.NET
d) None of the above

Answer: b) LINQ to SQL

74. Which of the following is a dependency injection framework used in .NET Core?
a) Autofac
b) Ninject
c) Simple Injector
d) All of the above

Answer: d) All of the above

75. Which of the following is a middleware component in .NET Core that is used to log messages?
a) ILogger
b) ConsoleLogger
c) DebugLogger
d) None of the above

Answer: a) ILogger

76. Which of the following is a feature in .NET Core that allows developers to build and run containerized applications?
a) Docker integration
b) Kubernetes integration
c) Azure integration
d) None of the above

Answer: a) Docker integration

77. Which of the following is a command-line tool used in .NET Core to create and manage database migrations?
a) EF Core
b) Dapper
c) SQL Server Management Studio
d) None of the above

Answer: a) EF Core

78. Which of the following is a library in .NET Core that is used to implement JSON serialization and deserialization?
a) Newtonsoft.Json
b) System.Text.Json
c) Json.NET
d) None of the above

Answer: b) System.Text.Json

79. Which of the following is a feature in .NET Core that allows developers to build and run microservices?
a) Service Fabric
b) Azure Functions
c) Docker containers
d) All of the above

Answer: d) All of the above

80. Which of the following is a framework in .NET Core that is used to build cross-platform desktop applications?
a) WinForms
b) WPF
c) Uno

Answer: c) Uno