Top 10 Senior .NET Engineer Interview Questions & Answers in 2024

1. Explain the concept of the ASP.NET Core middleware pipeline. How does it work, and what are some common use cases for middleware components?

The ASP.NET Core middleware pipeline is a series of components that handle HTTP requests and responses. Each middleware component can process, modify, or delegate the request. Common use cases include authentication, authorization, logging, and exception handling. Developers can customize the pipeline to suit the application's requirements, creating a flexible and modular architecture.

2. Discuss the advantages and disadvantages of using microservices architecture in .NET applications. When is it suitable, and what challenges may arise during development and maintenance?

Advantages:

• Scalability: Enables scaling individual services independently.
• Technology Diversity: Allows using different technologies for different services.
• Decentralization: Services can be developed, deployed, and maintained independently.

Disadvantages:

• Complexity: Introduces complexities in service discovery, communication, and data consistency.
• Operational Overhead: Managing and monitoring multiple services requires additional effort.
• Data Consistency: Ensuring data consistency across services can be challenging.

Microservices are suitable for large, complex applications with diverse requirements but require careful planning and management.

3. How can you optimize the performance of an Entity Framework Core application? Discuss techniques like eager loading, explicit loading, and caching strategies.

Eager Loading: Use the Include method to load related entities along with the main entity, reducing the number of database queries.

Explicit Loading: Utilize the Load method to explicitly load related entities on-demand, optimizing performance when certain relationships are not always required.

Caching Strategies: Implement caching mechanisms, such as query result caching or distributed caching, to reduce database round-trips and enhance application responsiveness.

4. Explain the role of the Actor Model in building concurrent and distributed systems. How can you implement the Actor Model in a .NET application using frameworks like Akka.NET?

The Actor Model is a programming model for building concurrent and distributed systems, where actors are independent entities that communicate through message passing. In .NET, Akka.NET is a framework that implements the Actor Model. Actors in Akka.NET are lightweight, and communication is achieved through messages. This model simplifies handling concurrency and scalability challenges by avoiding shared state and locks.

5. Discuss the concepts of Dapper and compare it to Entity Framework. In what scenarios would you choose Dapper over Entity Framework, and vice versa?

Dapper:

• Micro-ORM: Lightweight Object-Relational Mapping library.
• Performance: Faster than Entity Framework for certain scenarios due to its lightweight nature.
• Flexibility: Provides more control over SQL queries.

Entity Framework:

• Full-Featured ORM: Offers a comprehensive set of features for data access.
• Abstraction: Allows working with data using high-level abstractions like LINQ.
• Productivity: Easier to use for common scenarios and provides automatic tracking of changes.

Choose Dapper for performance-critical scenarios and control over SQL queries. Choose Entity Framework for rapid development and a more abstracted approach to data access.

6. How can you secure a .NET Core Web API? Discuss token-based authentication, authorization policies, and best practices for securing endpoints.

Token-Based Authentication:

• Use JWT (JSON Web Tokens) for token-based authentication.
• Implement a token issuance and validation mechanism.

Authorization Policies:

• Define policies for fine-grained access control.
• Apply policies using the [Authorize] attribute.

Best Practices:

• Use HTTPS to encrypt data in transit.
• Implement input validation to prevent common security vulnerabilities.
• Regularly update dependencies to address security vulnerabilities.

7. Discuss the benefits and challenges of implementing a GraphQL API in a .NET application. When is GraphQL a suitable choice, and how does it differ from traditional REST APIs?

Benefits:

• Efficiency: Clients can request only the data they need, reducing over-fetching.
• Flexibility: Single endpoint for multiple data types and queries.
• Real-Time Data: Supports real-time data updates through subscriptions.

Challenges:

• Learning Curve: Requires understanding of the GraphQL query language.
• Caching: Can be challenging to implement due to dynamic queries.
• Complexity: Overhead in certain scenarios with simpler requirements.

GraphQL is suitable for scenarios where flexibility and efficiency in data retrieval are priorities.

8. Explain the concepts of Blazor and WebAssembly in .NET Core. How does Blazor enable building interactive web applications, and what are the key advantages?

Blazor:

• Web Framework: Allows building interactive web applications using C# and .NET.
• Component-Based: Organizes UI elements into reusable components.
• Server-Side and WebAssembly: Supports both server-side rendering and client-side execution using WebAssembly.

WebAssembly:

• Binary Instruction Format: Executes code at near-native speed in modern web browsers.
• Platform Independence: Allows running code written in multiple languages in the browser.

Blazor brings the power of .NET to web development, enabling code sharing between client and server.

9. How does .NET Core support cross-platform development? Discuss the benefits and challenges of deploying .NET Core applications on different operating systems.

Cross-Platform Support:

• Platform-Independent Runtime: .NET Core runtime is cross-platform.
• Language Interoperability: Supports multiple languages, enhancing cross-platform compatibility.

Benefits:

• Flexibility: Deploy applications on Windows, Linux, or macOS.
• Cost-Efficiency: Reduces infrastructure costs with the ability to choose diverse hosting environments.

Challenges:

• Platform-Specific Considerations: Handling differences in filesystems, environment variables, and dependencies.

.NET Core provides a versatile framework for building applications that can run seamlessly on different platforms.

10. Discuss the principles of Domain-Driven Design (DDD) in .NET development. How can DDD concepts like aggregates, entities, and value objects improve the design and maintainability of a system?

Aggregates, Entities, and Value Objects:

• Aggregates: Group related entities and value objects, enforcing consistency boundaries.
• Entities: Objects with a distinct identity and mutable state.
• Value Objects: Objects without identity, representing concepts like dates or money.
• Ubiquitous Language: Shared vocabulary between developers and domain experts.
• Bounded Contexts: Define explicit boundaries for different parts of the system.
• Event Sourcing and CQRS: Techniques aligned with DDD principles for handling complex business logic.

By adhering to DDD principles, developers can create a more expressive and maintainable codebase that closely aligns with the business domain.