Interview Questions & Answer For Full Stack .NET Developer

Frequently Asked Full Stack Developer Interview Questions And Answers

Q 1. What are the different return types in MVC?

Answer

• Return View
• Return partial View
• Return Redirect
• Redirect To Action
• Return content
• Return JSON
• Return JavaScript
• Return File

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Q 2. What is the difference between ViewBag, ViewData, and TempData in MVC?

Answer

ViewBag is a dynamic object to pass the data from Controller to View. ViewData is a dictionary object to pass the data from Controller to View, where data is passed in the form of key-value pair. TempData is a dictionary object to pass the data from one action to another action in the same Controller or different Controllers. Usually, the TempData object will be stored in a session object. Tempdata is also required to typecast and for null checking before reading data from it.

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Q 3. What is routing & different types of routing in MVC?

Answer

Routing is a mechanism to process the incoming url that is more descriptive and gives the desired response. In this case, the URL is not mapped to specific files or folders, as was the case of earlier days' websites.

There are two types of routing (after the introduction of ASP.NET MVC 5).

1. A) Convention-based routing: To define this type of routing, we call MapRoute the method and set its unique name, url pattern and specify some default values.
2. B) Attribute-based routing: To define this type of routing, we specify the Route attribute in the controller's action method.

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Q 4. What is Polymorphism?

Answer

The word Polymorphism means having many forms. In simple words, we can define Polymorphism as the ability of a message to be displayed in more than one form. Polymorphism is a Greek word meaning "one name many forms". In other words, one object has many forms or has one name with multiple functionalities. "Poly" means many, and "morph" means forms. Polymorphism provides the ability for a class to have multiple implementations with the same name. It is one of the core principles of Object Oriented Programming after encapsulation and inheritance. In this article, you'll learn what Polymorphism is, how it works, and how to implement it in C#.

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Q 5. What are the different types of Polymorphism?

Answer

There are two types of Polymorphism, as below.

• Static Polymorphism
• Dynamic Polymorphism

Q 6. What is Boxing & Unboxing in C#?

Answer

Boxing and unboxing in C# allow developers to convert .NET data types from value type to reference type and vice versa. Converting a value type to a reference type is called boxing in C#, and converting a reference type to a value type is called unboxing in C#.

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Q 7. What is Partial class in C#?

Answer

A partial class splits the definition of a class over two or more source (.cs) files. You can create a class definition in multiple physical files, but it will be compiled as one class when the classes are compiled.

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Q 8. What is a sealed class in C#?

Answer

Sealed classes are used to restrict the inheritance feature of object-oriented programming. Once a class is defined as a sealed class, this class cannot be inherited. In C#, the sealed modifier declares a class as sealed. In Visual Basic .NET, the NotInheritable keyword serves the purpose of sealed. If a class is derived from a sealed class, the compiler throws an error.

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Q 9. What is an abstract class in C#?

Answer

An abstract class is an incomplete class or special class that can't be instantiated. The purpose of an abstract class is to provide a blueprint for derived classes and set some rules that the derived classes must implement when they inherit an abstract class. We can use an abstract class as a base class; all derived classes must implement abstract definitions. An abstract method must be implemented in all non-abstract classes using the override keyword. After overriding the abstract method is in the non-Abstract class. We can derive this class in another class and override the same abstract method with it.

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Q10. What is Interface in C#?

Answer

An interface looks like a class but has no implementation. The only thing it contains are declarations of events, indexers, methods, and/or properties. The reason interfaces only provide declarations is that they are inherited by structs and classes that must provide an implementation for each interface member declared.

So, what are interfaces good for if they don't implement functionality? They're great for putting together plug-and-play-like architectures where components can be interchanged at will. Since all interchangeable components implement the same interface, they can be used without extra programming. The interface forces each component to expose specific public members that will be used in a certain way.

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Q 11. What is Inheritance in C#?

In C#, inheritance allows us to create a new class from an existing class. It is a key feature of Object-Oriented Programming (OOP). The class from which a new class is created is the base class (parent or superclass). And the new class is called the derived class (child or subclass). The derived class inherits the fields and methods of the base class. This helps with the code reusability in C#.

Q 12. What is encapsulation in C#?

Encapsulation, in the context of C#, refers to an object's ability to hide data and behavior that is unnecessary to its user. Encapsulation enables a group of properties, methods, and other members to be considered a single unit or object.

The following are the benefits of encapsulation,

• Protection of data from accidental corruption
• Specification of the accessibility of each of the members of a class to the code outside the class
• Flexibility and extensibility of the code and reduction in complexity
• Lower coupling between objects and hence improvement in code maintainability
• Encapsulation is used to restrict access to the members of a class to prevent the user of a given class from manipulating objects in ways that are not intended by the designer. While encapsulation hides the internal implementation of the functionalities of the class without affecting the overall functioning of the system, it allows the class to service a request for functionality and add or modify its internal structure (data or methods) to suit changing requirements.
• Encapsulation is also known as information hiding

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Q. 13. What is the ref keyword in C#?

The ref keyword passes arguments by reference. Any changes made to this argument in the method will be reflected in that variable when the control returns to the calling method.

C# supports value type and reference type data types. By default, the value type variable is passed by value, and the reference type variable is passed by reference from one method to another in C#.

The ref keyword in C# is used for passing or returning references of values to or from Methods. It means that any change made to a value passed by reference will reflect this change since you are modifying the value at the address and not just the value. It can be implemented in the following cases:

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Q 14. What is method overloading in C#?

Method overloading allows programmers to use multiple methods with the same name. The methods are differentiated by their number and type of method arguments. Method overloading is an example of the polymorphism feature of an object-oriented programming language.

Method overloading can be achieved by the following,

• Changing the number of parameters in a method
• Changing the order of parameters in a method
• By using different data types for parameters

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Q. 15. What is method overriding in C#?

Overriding can be defined as being able to change or augment the behavior of methods in classes, known as overriding their logic; it is one of the most powerful aspects of Object Oriented Programming.

Method Overriding in C# is similar to the virtual function in C++. Method Overriding is a technique that allows invoking functions from another class (base class) in the derived class. Creating a method in the derived class with the same signature as a method in the base class is called method overriding.

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Q. 16. What is a static class in C#?

A static class in C# is a class that cannot be instantiated. A static class can only contain static data members, including static methods, static constructors, and static properties. In C#, a static class is a class that cannot be instantiated. In C#, a static class is a class that cannot be instantiated. The main purpose of using static classes in C# is to provide blueprints of its inherited classes. Static classes are created using the static keyword in C# and .NET. A static class can contain static members only. You can't create an object for the static class.

Advantages of Static Classes

• If you declare any member as a non-static member, you will get an error.
• When you try to create an instance to the static class, it again generates a compile-time error because the static members can be accessed directly with their class name.
• The static keyword is used before the class keyword in a class definition to declare a static class.
• Static class members are accessed by the class name followed by the member name.

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Q. 17. How can we call a method without calling the object?

We can call a static method by using the ClassName. methodName. The best example of the static method is the main() method. It is called without creating the object.

Q. 18. What is Partial View in MVC?

Partial View in ASP.NET MVC is a special view that renders a portion of view content. It is just like a user control of a web form application. Partial can be reusable in multiple views. It helps us to reduce code duplication. In other words, a partial view enables us to render a view within the parent view. The Partial View is instantiated with its copy of a ViewDataDictionary object available with the parent view so that the partial View can access the data of the parent view.

If we make the change in this data (ViewDataDictionary object), the parent view's data is not affected. Generally, the Partial rendering method of the View is used when related data we want to render in a partial view is part of our model.

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Q. 19. What is the difference between a partial and a main view?

Partial View () is a Reusable view, but the View () is a single page that will render a normal .aspx page. The View can contain a complete markup which may contain a master view(or master page) with all the design(s) etc., whereas the Partial View is only a portion of the page or a small markup which don't have a master page. It is used as user control in MVC and can be used in more than one View.

Q. 20. What is indexing in an SQL server?

SQL Indexes are used in relational databases to quickly retrieve data. They are similar to indexes at the end of the books whose purpose is to find a topic quickly. SQL provides Create Index, Alter Index, and Drop Index commands that are used to create a new index, update an existing index, and delete an index in SQL Server. Data is internally stored in a SQL Server database in "pages" where the size of each page is 8KB.

A continuous 8 pages are called an "Extent". When we create the table, then one extent will be allocated for two tables, and when that extent is computed, it is filled with the data, then another extent will be allocated, and this extent may or may not be continuous to the first extent.

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Q. 21. What is null in SQL?

The IS NOT NULL operator is used to test for non-empty values (NOT NULL values).

SELECT column_names
FROM table_name

WHERE column_name IS NULL;

Q. 22. What are aggregate functions and scalar functions in SQL?

For doing operations on data, SQL has many built-in functions; they are categorized into two categories and further sub-categorized into seven different functions under each category. The categories are,

Aggregate functions

These functions are used to do operations from the values of the column, and a single value is returned.

1. AVG()
2. COUNT()
3. FIRST()
4. LAST()
5. MAX()
6. MIN()
7. SUM()

Scalar functions

These functions are based on user input, and these, too, return a single value.

1. UCASE()
2. LCASE()
3. MID()
4. LEN()
5. ROUND()
6. NOW()
7. FORMAT()

Q. 23. What are the different types of Authentication in SQL Servers?

In simple words, Authentication means identifying a user or a person based on their username and password. In the same way, SQL Server also authenticates its users by their credentials. SQL Server uses the following 2 types of Authentication.

• Windows Authentication.
• SQL Server Authentication.

Q. 24. What is Full-stack development?

Full-stack development refers to the ability to work on both the front-end and back-end parts of a web application. A full-stack developer is proficient in both client-side technologies (HTML, CSS, JavaScript) and server-side technologies (such as .NET, Node.js, or Ruby on Rails). They have the knowledge and skills to handle the complete development process, including user interface design, server-side logic, database management, and deployment.

Q. 25. What is the difference between front-end and back-end development?

Front-end development focuses on the client side of a web application, dealing with the user interface, user experience, and interactions. It primarily involves HTML, CSS, and JavaScript. Back-end development, on the other hand, involves the server side of the application, handling data storage, processing, and communication with databases or external services. It often includes technologies like .NET, PHP, Python, or Java.

Q. 26. What are the advantages of using the .NET framework?

• The .NET framework provides several advantages, including a vast library of pre-built components and classes, which speeds up development.
• It supports multiple languages (C#, VB.NET, F#), providing flexibility to developers.
• .NET offers great performance, security, and scalability and integrates well with Microsoft products and services. Additionally, .NET has a large, active community offering extensive support and resources.

Q. 27. Explain the difference between ASP.NET Web Forms and ASP.NET MVC.

• ASP.NET Web Forms is a web application framework that follows a visual drag-and-drop model for building web pages.
• It uses a concept called "view state" to maintain the state of control between postbacks.
• ASP.NET MVC, on the other hand, follows the Model-View-Controller architectural pattern.
• It provides greater control over HTML, promotes separation of concerns, and enables testability and flexibility.
• MVC is generally preferred for modern web development, while Web Forms is suitable for legacy applications or rapid development scenarios.

Q. 28. What is Entity Framework, and how does it relate to database operations in .NET?

• Entity Framework (EF) is an Object-Relational Mapping (ORM) framework provided by Microsoft.
• It simplifies database operations by allowing developers to work with relational data using object-oriented programming concepts.
• EF maps database tables to classes and provides a set of APIs to perform CRUD (Create, Read, Update, Delete) operations on the database.
• It also handles the generation of SQL queries, change tracking, and data caching.

Q. 29. What is the role of the Global.asax file in an ASP.NET application?

• The Global.asax file serves as the application-level event handler in an ASP.NET application.
• It contains events such as Application_Start, Application_End, Session_Start, and Session_End.
• Developers can use these events to perform application-level initialization tasks, set up global variables, handle application-level errors, and manage session-related events.

Q. 30. How do you handle errors and exceptions in .NET?

• In .NET, errors and exceptions can be handled using try-catch blocks.
• Code likely to throw an exception is placed within the try block, and any potential exceptions are caught and handled in the catch block.
• Additionally, .NET provides a global exception handler through the Application_Error event in the Global.asax file, allowing developers to handle unhandled exceptions at the application level.

Q. 31. Explain the concept of model binding in ASP.NET MVC.

• Model binding is the process of mapping incoming request data to the parameters of a controller action method in ASP.NET MVC.
• When a request is made to a controller action, the MVC framework automatically binds the values from the request (query string, form data, route data) to the corresponding action method parameters.
• It simplifies the process of extracting data from HTTP requests and reduces the need for manual data extraction.

Q. 32. What is the purpose of the App_Start folder in an ASP.NET MVC project?

• The App_Start folder in an ASP.NET MVC project is used to store various configuration classes that are automatically executed during application startup.
• These classes are responsible for configuring different aspects of the application, such as routing, bundling, filtering, and Authentication.
• Examples of files within the App_Start folder include RouteConfig.cs, BundleConfig.cs, and FilterConfig.cs.

Q. 33. Explain the concept of dependency injection and how it is used in .NET.

• Dependency injection is a design pattern that promotes loose coupling and modularization in software development.
• It involves injecting dependencies (objects or services) into a class rather than having the class create or manage them directly. In .NET, dependency injection is commonly implemented using frameworks like Microsoft Dependency Injection (DI) or third-party libraries like Ninject or Unity.
• It allows for easier testing and better code maintainability and facilitates the composition of complex systems from smaller, reusable components.

Q. 34. What is the difference between an abstract class and an interface in .NET?

• In .NET, an abstract class is a class that cannot be instantiated and is typically used as a base class for deriving other classes.
• It can contain both concrete and abstract members, and derived classes must provide implementations for the abstract members.
• An interface, on the other hand, is a contract that defines a set of methods and properties that a class must implement.
• Unlike an abstract class, an interface cannot contain any implementation details and is implemented explicitly by classes.

Q. 35. How do you implement Authentication and authorization in ASP.NET?

• In ASP.NET, Authentication refers to the process of identifying and validating the user, while authorization determines the user's access rights to various resources.
• Authentication can be implemented using different mechanisms such as Forms Authentication, Windows Authentication, or OAuth. Authorization is typically achieved through roles, claims, or attribute-based authorization. ASP.NET provides features like authentication middleware, role-based security, and the Authorize attribute to handle these aspects.

Q. 36. What are the different types of caching available in ASP.NET?

ASP.NET provides several caching mechanisms to improve performance and reduce database or server load. These include:

1. Output Caching: Caches the entire output of a page or user control.
2. Fragment Caching: Caches specific parts or fragments of a page.
3. Data Caching: Stores frequently accessed data in memory.
4. Object Caching: Caches custom objects to reduce object creation and improve performance.
5. Distributed Caching: Uses distributed cache systems like Redis or Memcached to share cache across multiple servers.

Q. 37. How does AJAX work in ASP.NET?

AJAX (Asynchronous JavaScript and XML) allows for partial page updates without a full page reload, providing a smoother user experience.

In ASP.NET, AJAX can be implemented using the Microsoft AJAX Library (UpdatePanel, ScriptManager) or through the use of JavaScript libraries like jQuery and sending asynchronous HTTP requests to the server using the XMLHttpRequest object or the newer Fetch API.

Q. 38. Explain the concept of middleware in ASP.NET Core.

Middleware in ASP.NET Core refers to components that participate in processing HTTP requests and responses. Each middleware component can examine, modify, or short-circuit the request/response pipeline. Examples of middleware include Authentication, logging, routing, exception handling, and static file serving. The order in which middleware components are registered determines the order in which they are executed.

Q. 39. What are the advantages of using ASP.NET Core over previous versions?

ASP.NET Core offers several advantages over previous versions of ASP.NET, including:

1. Cross-platform support: ASP.NET Core can run on Windows, Linux, and macOS, allowing for more deployment options.
2. High-performance: It is optimized for performance, with features like built-in dependency injection and middleware pipeline.
3. Modular and lightweight: ASP.NET Core allows for a granular selection of components, reducing the overhead of unused features.
4. Improved flexibility: It supports multiple development models (MVC, Web API, Razor Pages) and can be easily integrated with front-end frameworks like Angular or React.
5. Open-source and community-driven: ASP.NET Core is open-source, with an active community that provides support, extensions, and frequent updates.

Q. 40. Explain the concept of routing in ASP.NET MVC.

• Routing in ASP.NET MVC is the process of mapping incoming URLs to controller actions.
• It determines which controller and action method should handle a particular request.
• The routing configuration is typically defined in the RouteConfig.cs file, where developers can specify URL patterns and route parameters. Routing allows for clean and SEO-friendly URLs by mapping them to appropriate actions, which enhances the overall user experience.

Q. 41. What is the role of a view model in an ASP.NET MVC application?

• A view model in ASP.NET MVC is a class that is specifically designed to transfer data between the controller and the View.
• It encapsulates the data required by the View, ensuring that the View has all the necessary information for rendering without directly exposing the model or domain objects.
• The view model helps in maintaining the separation of concerns and allows for better control over the data displayed in the View.

Q. 42. How do you implement validation in ASP.NET MVC?

• In ASP.NET MVC, validation can be implemented using Data Annotations and attributes applied to model properties.
• These attributes define validation rules such as required fields, string length restrictions, and regular expression patterns.
• Additionally, client-side validation can be enabled using JavaScript libraries like jQuery Validation.
• Validation errors can be displayed in the View using the ValidationMessageFor or ValidationSummary helpers.

Q. 43. Explain the concept of RESTful APIs and how they are implemented in .NET.

• REST (Representational State Transfer) is an architectural style for designing networked applications.
• RESTful APIs follow a set of principles, including stateless communication, resource-based URLs, and standard HTTP methods (GET, POST, PUT, DELETE) to perform CRUD operations.
• In .NET, RESTful APIs can be implemented using technologies like ASP.NET Web API or ASP.NET Core Web API, which provide features and frameworks for building and exposing RESTful endpoints.

Q. 44. What is the role of the Global.asax.cs file in an ASP.NET application?

• The Global.asax.cs file in an ASP.NET application serves as the code-behind file for the Global.asax file.
• It contains application-level event handlers and logic, such as Application_Start, Application_End, Session_Start, Session_End, and more. Developers can use these events to perform tasks like application initialization, cleanup, session management, error handling, and other application-level operations.

Q. 45. How do you implement session management in ASP.NET?

• Session management in ASP.NET is handled through the HttpSessionState object, which represents a user-specific session.
• The session can store data that needs to be persisted across multiple requests, such as user preferences or shopping cart information.
• Session data can be accessed and modified using the Session object, and it can be configured to use different session storage mechanisms, such as in-process, out-of-process (using SQL Server or State Server), or using distributed cache systems.

Q. 46. What are the different types of HTTP status codes and their meanings?

HTTP status codes indicate the status of an HTTP request and response. Some common status codes include:

1. 200 OK: The request was successful.
2. 404 Not Found: The requested resource was not found.
3. 500 Internal Server Error: An unexpected error occurred on the server.
4. 401 Unauthorized: The request requires Authentication.
5. 403 Forbidden: The server understood the request, but access is forbidden.
6. 302 Found: The requested resource has been temporarily moved to a different URL.

There are many other status codes that convey different meanings, and each one serves a specific purpose in the HTTP protocol.

Q. 47. Explain the concept of inversion of control (IoC) and how it is used in .NET.

• Inversion of Control (IoC) is a software design principle that aims to invert the control of object creation and management.
• Instead of creating objects directly within a class, IoC allows the dependencies to be injected into the class from an external source, usually through constructor parameters or properties.
• In .NET, IoC containers like Microsoft Dependency Injection (DI) framework, Ninject, or Unity manage object creation, resolve dependencies, and achieve loose coupling between components.

Q. 48. What is the purpose of the Web.config file in an ASP.NET application?

• The Web.config file in an ASP.NET application is a configuration file that stores various settings for the application.
• It contains information such as connection strings, application-level settings, HTTP modules and handlers, session state configuration, security settings, and more.
• The Web.config file allows developers to modify application behavior without recompiling the code, providing flexibility and easy maintenance.

Q. 49. How do you handle cross-site scripting (XSS) attacks in .NET?

• Cross-site scripting (XSS) attacks can be prevented in .NET by properly encoding user input before displaying it in the View.
• The ASP.NET MVC framework automatically performs HTML encoding of user input when rendered in the View, which helps prevent XSS attacks. Using output escaping techniques, such as the AntiXSS library, can further enhance protection against XSS vulnerabilities.

Q. 50. Explain the concept of asynchronous programming in .NET.

• Asynchronous programming in .NET allows for the execution of non-blocking code, enabling responsiveness and scalability in applications.
• It involves performing asynchronously without blocking the main thread, allowing other operations to continue. Asynchronous programming in .NET can be achieved using features like async and await keywords, Task and Task<T> types, and the asynchronous programming model (APM) or task-based asynchronous pattern (TAP).

Q. 51. What is the role of the .NET Common Language Runtime (CLR)?

• The Common Language Runtime (CLR) is the execution engine of the .NET framework.
• It provides a runtime environment where .NET applications are executed.
• The CLR is responsible for memory management (garbage collection), code execution, exception handling, security enforcement, and thread management. It enables the interoperability of different .NET languages and provides a common execution environment for all .NET applications.

Q. 52. How do you deploy a .NET application to a web server?

• Deploying a .NET application to a web server typically involves the following steps:

1. Build the application: Compile the application into its binary form.
2. Prepare the server: Set up the web server (IIS, Apache, etc.) with the necessary dependencies and configurations.
3. Publish the application: Create a publish profile and use Visual Studio Publish or command-line tools (dotnet publish) to generate the deployment-ready files.
4. Copy the files: Copy the published files to the web server, either manually or through automated deployment tools.
5. Configure the server: Configure the webserver to host the application, including setting up application pools, virtual directories, and any required environment variables or settings.
6. Test the deployment: Ensure that the application runs correctly on the web server by testing its functionality and verifying that it meets the desired requirements.

Q. 53. How do you optimize performance in a .NET application?

Optimizing performance in a .NET application can involve various techniques, including:

1. Efficient database access: Optimize database queries, use appropriate indexes, and consider caching strategies to minimize round trips to the database.
2. Code profiling: Identify bottlenecks and performance issues using profiling tools, such as Visual Studio Profiler or third-party profilers.
3. Caching: Implement caching mechanisms to store frequently accessed data in memory, reducing the need for expensive computations or database queries.
4. Asynchronous programming: Utilize asynchronous programming techniques to allow concurrent execution of operations and avoid blocking the main thread.
5. Code optimization: Optimize code by eliminating unnecessary loops, reducing object allocations, using efficient algorithms and data structures, and avoiding resource-intensive operations within loops.
6. Minification and bundling: Minify and bundle JavaScript and CSS files to reduce the overall file size and optimize network transfer.
7. Load balancing and scaling: Implement load balancing and scaling strategies to distribute the application load across multiple servers, ensuring optimal performance under heavy traffic.
8. Profiling and performance testing: Regularly test and measure application performance using load testing tools to identify areas for improvement.

This is all about the article. Thanks for reading.