Top ASP.NET Interview Questions（2025）

Question: What is Entity Framework in ASP.NET?

Answer:

Entity Framework (EF) is an Object-Relational Mapping (ORM) framework provided by Microsoft that allows developers to interact with databases using .NET objects. It simplifies data access by enabling you to work with databases in a more object-oriented way, reducing the need for writing raw SQL queries or handling low-level database operations manually. EF is used primarily in ASP.NET applications to interact with relational databases such as SQL Server.

Entity Framework provides a set of tools and APIs that allow developers to map database tables to .NET classes and allows them to query and manipulate data using LINQ (Language Integrated Query), which is much more intuitive than SQL.

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Key Features of Entity Framework:

1. Object-Relational Mapping (ORM):

   • EF maps database tables to classes (called entities) and rows in tables to objects.
   • It enables developers to work with database data in the form of objects and collections.
   • You don’t need to write SQL queries directly unless you need complex or highly specific operations.

2. Code-First, Database-First, and Model-First Approaches:

   • Code-First: You write C# classes first, and EF generates the database schema from these classes.
   • Database-First: You generate classes based on an existing database schema.
   • Model-First: You design the model visually, and EF generates both the classes and the database schema.

3. LINQ Support:

   • EF allows you to use LINQ (Language Integrated Query) to write queries in C# or VB.NET, making it easier to interact with data in a more readable and maintainable way.
   • LINQ queries can be directly translated into SQL by EF, enabling easier and safer database queries.

4. Automatic Change Tracking:

   • EF tracks changes made to objects in memory and automatically generates SQL INSERT, UPDATE, or DELETE statements to synchronize changes with the database.
   • This eliminates the need for manual SQL statements to persist changes to the database.

5. Lazy Loading:

   • EF supports lazy loading, where related data (such as navigation properties) is loaded only when accessed, improving performance by loading data only when necessary.
   • However, developers can choose to disable lazy loading if they prefer eager or explicit loading.

6. Migrations:

   • Entity Framework supports migrations, which allow you to version and evolve your database schema over time without losing existing data. You can use migrations to update the database schema as your models change.
   • This is particularly useful when working with Code-First, as it helps in evolving the database schema alongside your code.

7. Transactions:

   • EF automatically handles transactions in a unit of work. It groups a set of database operations into a single transaction to ensure consistency and integrity.
   • You can also manage transactions manually if needed, providing flexibility for more advanced scenarios.

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Types of Entity Framework:

1. Entity Framework 6 (EF6):

   • This is the traditional version of Entity Framework, which runs on .NET Framework.
   • EF6 provides all the core features such as change tracking, migrations, LINQ support, and more.
   • It is widely used in older applications that are still running on the .NET Framework.

2. Entity Framework Core (EF Core):

   • EF Core is a cross-platform version of Entity Framework that works with .NET Core and the .NET 5/6+ ecosystem.
   • It is a lightweight, modular, and high-performance version of EF, designed for modern applications.
   • EF Core has additional features like in-memory databases, better support for non-relational databases (e.g., NoSQL databases like Cosmos DB), and performance improvements, but it may lack some features that were available in EF6.
   • EF Core is actively being improved and is the recommended option for new projects using .NET Core.

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Common Operations in Entity Framework:

1. CRUD Operations:

   • Create: Inserting data into the database.

     var product = new Product { Name = "Apple", Price = 1.99 };
     context.Products.Add(product);
     context.SaveChanges();

   • Read: Querying data from the database using LINQ.

     var products = context.Products.Where(p => p.Price > 1.00).ToList();

   • Update: Modifying existing data.

     var product = context.Products.Find(1);
     product.Price = 2.99;
     context.SaveChanges();

   • Delete: Removing data.

     var product = context.Products.Find(1);
     context.Products.Remove(product);
     context.SaveChanges();

2. Relationships:

   • EF supports relationships between entities such as one-to-many, many-to-many, and one-to-one.
   • Example of a one-to-many relationship:

     public class Category
     {
         public int CategoryId { get; set; }
         public string Name { get; set; }
         public ICollection<Product> Products { get; set; }
     }

     In this example, one category can have many products.

3. Lazy Loading (if enabled):

   • When you query an entity, related entities are loaded only when accessed.

     var category = context.Categories.FirstOrDefault();
     var products = category.Products; // Products are loaded when accessed

4. Eager Loading (explicitly load related data):

   • Use Include to explicitly load related data in a single query.

     var category = context.Categories.Include(c => c.Products).FirstOrDefault();

5. Migrations:

   • Migrations help you keep the database schema in sync with your model. You can add, remove, or modify tables and columns without manually writing SQL scripts.

     # Add a migration
     dotnet ef migrations add InitialCreate
     
     # Apply migrations to the database
     dotnet ef database update

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Benefits of Using Entity Framework:

1. Productivity: EF automates many tedious tasks, such as database queries and transaction management, allowing developers to focus more on business logic.

2. Code-First Development: EF allows you to design the model in code first, which can be a more agile and iterative approach.

3. Database-First Approach: EF also supports database-first development, which is useful when working with legacy databases or databases that already exist.

4. LINQ Support: Querying data through LINQ results in cleaner and more maintainable code. EF will automatically translate LINQ queries into efficient SQL queries.

5. Cross-Platform (EF Core): With EF Core, you can build cross-platform applications that work on Windows, Linux, and macOS, making it suitable for modern application development.

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Example of Using Entity Framework in an ASP.NET MVC Application:

Model Class (Code-First Approach):

public class Product
{
    public int ProductId { get; set; }
    public string Name { get; set; }
    public decimal Price { get; set; }
}

DbContext Class:

public class ApplicationDbContext : DbContext
{
    public DbSet<Product> Products { get; set; }
}

Controller:

public class ProductsController : Controller
{
    private readonly ApplicationDbContext _context;

    public ProductsController(ApplicationDbContext context)
    {
        _context = context;
    }

    public IActionResult Index()
    {
        var products = _context.Products.ToList();
        return View(products);
    }
}

View (Index.cshtml):

@model IEnumerable<Product>

<table>
    <tr>
        <th>Name</th>
        <th>Price</th>
    </tr>
    @foreach (var product in Model)
    {
        <tr>
            <td>@product.Name</td>
            <td>@product.Price</td>
        </tr>
    }
</table>

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Conclusion:

Entity Framework (EF) is a powerful ORM framework that simplifies database operations in ASP.NET applications. It provides an abstraction layer that allows developers to interact with databases using C# objects rather than SQL queries. EF supports multiple workflows, including Code-First, Database-First, and Model-First, and is actively used in both ASP.NET MVC and ASP.NET Core MVC applications for data access. Whether you’re building web applications or APIs, EF streamlines data management and helps developers focus on building features rather than worrying about SQL or database operations.

Question: What are the advantages of using ASP.NET Core over traditional ASP.NET?

Answer:

ASP.NET Core is a significant redesign of the traditional ASP.NET framework. It introduces several advantages, particularly in terms of performance, flexibility, scalability, and cross-platform capabilities. Below are some key benefits of using ASP.NET Core over the traditional ASP.NET framework:

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1. Cross-Platform Support

• ASP.NET Core is cross-platform, meaning it can run on Windows, Linux, and macOS. This is a major advantage for developers who need to deploy applications on different operating systems or build applications for a diverse set of environments.
• Traditional ASP.NET (ASP.NET Framework) runs only on Windows and relies on IIS (Internet Information Services) for deployment.

Benefit:

• Allows developers to create cross-platform web applications, giving more flexibility in deployment environments and enabling the use of open-source technologies.

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2. Performance Improvements

• ASP.NET Core is designed with performance in mind and has shown significant performance improvements over the traditional ASP.NET framework. The new Kestrel web server (used by ASP.NET Core) is much faster and more efficient than the older IIS server used in traditional ASP.NET.
• ASP.NET Core has been optimized for minimal overhead, making it much more lightweight and scalable compared to ASP.NET, especially in high-load scenarios.

Benefit:

• Faster execution, better memory utilization, and higher throughput for web applications.

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3. Modular and Lightweight

• ASP.NET Core is highly modular, meaning that you can include only the packages and features you need for your application. This is different from the traditional ASP.NET framework, which comes with a monolithic, all-in-one approach.
• In ASP.NET Core, the framework is split into smaller NuGet packages, and you can install only the required ones, making your application lighter and easier to manage.

Benefit:

• More efficient resource usage, faster startup times, and easier maintenance due to the modular architecture.

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4. Unified MVC and Web API Framework

• In ASP.NET Core, the MVC (Model-View-Controller) and Web API frameworks are unified into a single framework. In traditional ASP.NET, MVC and Web API were separate components, which often led to duplicated code and inconsistencies when building API-based web applications.
• In ASP.NET Core, the same controller can be used to serve both web pages (via views) and API responses (via JSON/XML), providing a more consistent development experience.

Benefit:

• Simplified architecture, less duplication of code, and better developer productivity when building both web pages and APIs.

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5. Dependency Injection (DI) Built-In

• ASP.NET Core has dependency injection (DI) built-in at the framework level. DI is a design pattern that helps make your application more modular and testable by promoting loose coupling between components.
• In traditional ASP.NET, DI is available, but it requires third-party libraries (e.g., Unity, Autofac) or configuration work to implement it effectively.

Benefit:

• Built-in dependency injection simplifies the architecture of applications, increases testability, and promotes loose coupling.

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6. Cloud-Ready and Microservices Architecture

• ASP.NET Core is optimized for cloud deployment and microservices architectures. With features like Docker support, Kubernetes compatibility, and configuration options for cloud-based services (like Azure), it’s much easier to deploy and scale applications in the cloud.
• ASP.NET Core has built-in tools for handling distributed applications, making it more suitable for cloud-based or microservices-based applications.
• Traditional ASP.NET was not as well-suited for microservices or cloud-native architectures out of the box.

Benefit:

• Ready for cloud deployments, scalability, and microservices architecture, helping developers build modern, distributed applications.

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7. Simplified Configuration System

• ASP.NET Core introduces a flexible configuration system that supports multiple configuration sources such as environment variables, JSON files, command-line arguments, and user secrets.
• The traditional ASP.NET framework had a less flexible configuration system, relying heavily on Web.config files for settings and configurations.

Benefit:

• More flexible and dynamic configuration management, especially useful for cloud environments and containerized applications.

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8. Open-Source and Community-Driven

• ASP.NET Core is open-source and hosted on GitHub. It has a large and active community of developers contributing to its improvement and ensuring it stays up-to-date with the latest technologies.
• ASP.NET (the traditional version) was not open-source until .NET Core was introduced. While Microsoft has made ASP.NET more open over time, ASP.NET Core is truly community-driven with transparent development.

Benefit:

• Active community support, faster bug fixes, community contributions, and increased collaboration among developers.

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9. Cross-Platform Development with .NET Core

• ASP.NET Core is built on top of .NET Core, which is a cross-platform runtime that allows you to run applications on multiple operating systems like Windows, Linux, and macOS.
• The traditional ASP.NET is tied to the .NET Framework, which only works on Windows, limiting its flexibility and deployment options.

Benefit:

• Cross-platform compatibility allows developers to build and deploy applications on multiple platforms without worrying about OS constraints.

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10. No IIS Dependency

• ASP.NET Core doesn’t require IIS for hosting. The Kestrel web server that ships with ASP.NET Core is a lightweight and cross-platform web server that can be used independently or behind other web servers like Nginx or Apache.
• Traditional ASP.NET relies on IIS as the primary web server, which can be limiting for non-Windows hosting environments.

Benefit:

• Flexibility in choosing a hosting environment and better performance with Kestrel.

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11. Built-In Support for Modern Web Development

• ASP.NET Core supports modern web development practices out of the box. This includes built-in support for modern JavaScript frameworks, SPA (Single Page Application) architectures, and easy integration with tools like Angular, React, or Vue.js.
• Traditional ASP.NET requires more manual configuration and tooling for modern front-end frameworks and SPA support.

Benefit:

• Streamlined workflow for building modern web applications with integrated front-end and back-end development.

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12. Improved Security

• ASP.NET Core offers several security improvements over the traditional framework, such as built-in support for modern authentication protocols like OAuth2 and OpenID Connect, as well as enhanced support for HTTPS and CORS.
• It also offers cross-site scripting (XSS) and cross-site request forgery (CSRF) protections, which help build secure web applications.

Benefit:

• Better security features and standards, making it easier to develop secure applications.

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Summary of Key Advantages:

Feature	ASP.NET Core	Traditional ASP.NET
Cross-Platform	Yes (Windows, Linux, macOS)	No (Windows only)
Performance	High performance (optimized Kestrel server)	Lower performance (relies on IIS)
Modular and Lightweight	Yes, with modular packages	No, monolithic framework
Unified MVC and Web API	Yes, both are part of the same framework	Separate MVC and Web API frameworks
Dependency Injection (DI)	Built-in DI support	Requires third-party libraries
Cloud-Ready	Built for cloud and microservices	Less suitable for modern cloud-native architectures
Configuration System	Flexible and supports various sources	Web.config based, less flexible
Open-Source	Yes, open-source and community-driven	Not open-source
Hosting	Kestrel (cross-platform), can be used with Nginx/Apache	IIS only
Modern Web Support	Built-in support for SPA and modern JavaScript frameworks	Requires external configuration for modern web support

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Conclusion:

ASP.NET Core offers several advantages over traditional ASP.NET, especially in terms of cross-platform support, performance, and scalability. It is more flexible, modern, and optimized for cloud-native applications, making it a better choice for building web APIs, microservices, and cross-platform applications. If you are starting a new project or upgrading an existing application, ASP.NET Core is the recommended framework due to its numerous benefits and active community support.

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