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

1. Explain the concept of Asynchronous Programming in .NET. How does the async/await pattern work, and what are its advantages?

Asynchronous Programming in .NET allows non-blocking execution, improving application responsiveness. The async/await pattern simplifies asynchronous code by marking methods as asynchronous and awaiting the completion of asynchronous tasks. Advantages include enhanced scalability, improved responsiveness, and efficient resource utilization.

2. Discuss the role of Dependency Injection (DI) in ASP.NET Core. How does it promote modularity, and what are the key components involved in DI?

Dependency Injection in ASP.NET Core promotes loose coupling between components by injecting dependencies into classes rather than hardcoding them. Key components include:

• Service: The dependency to be injected.
• Client: The class receiving the dependency.
• Container: The built-in DI container that manages the injection.

DI enhances modularity, testability, and maintainability by reducing dependencies and making components more reusable.

3. How can you implement and handle transactions in ADO.NET? Discuss the significance of transactions in database operations.

Transactions in ADO.NET ensure the integrity of database operations by either committing or rolling back a series of related actions as a single unit. Key concepts include:

• SqlConnection and SqlTransaction: Used to initiate and manage transactions.
• Commit and Rollback: Methods to finalize or undo a transaction.

Transactions are vital for maintaining database consistency, especially in scenarios where multiple operations must succeed or fail together.

4. Discuss the differences between Value Types and Reference Types in C#. Provide examples and scenarios where each type is commonly used.

• Value Types: Contain the actual data, and instances of value types are stored directly in memory. Examples include integers (int), floating-point numbers (float), and structs.
• Reference Types: Contain a reference to the memory location where the data is stored. Examples include classes, arrays, and interfaces.

Value types are suitable for small, immutable data, while reference types are used for larger, mutable objects.

5. How can you optimize performance in an ASP.NET application? Discuss techniques such as output caching, bundling, and minification.

Optimizing performance in ASP.NET involves various techniques:

• Output Caching: Caches the HTML output of a page.
• Bundling: Combines multiple CSS or JavaScript files into a single file.
• Minification: Reduces the size of CSS or JavaScript files by removing unnecessary characters.

These techniques reduce server load, bandwidth usage, and improve page load times.

6. Explain the principles of SOLID, and discuss how these principles contribute to writing maintainable and scalable .NET applications.

SOLID is an acronym for five design principles:

• Single Responsibility Principle (SRP): A class should have only one reason to change.
• Open/Closed Principle (OCP): Software entities should be open for extension but closed for modification.
• Liskov Substitution Principle (LSP): Subtypes should be substitutable for their base types.
• Interface Segregation Principle (ISP): A class should not be forced to implement interfaces it does not use.
• Dependency Inversion Principle (DIP): High-level modules should not depend on low-level modules; both should depend on abstractions.

Applying SOLID principles leads to modular, maintainable, and scalable code by promoting a clean separation of concerns.

7. How can you secure sensitive information, such as connection strings, in a .NET application? Discuss best practices for managing secrets.

Secure sensitive information in a .NET application using techniques such as:

• Configuration Encryption: Encrypt connection strings or sensitive data in the configuration files using tools like aspnet_regiis.
• Azure Key Vault: Store secrets in Azure Key Vault and access them securely in the application.

Avoid hardcoding secrets, utilize secure storage options, and follow the principle of least privilege.

8. Explain the concepts of Garbage Collection in .NET. How does the Common Language Runtime (CLR) manage memory, and what strategies can you employ to optimize memory usage?

Garbage Collection in .NET automatically reclaims memory occupied by objects that are no longer in use. The CLR uses a generational garbage collector with three generations (Gen0, Gen1, and Gen2). Strategies to optimize memory usage include:

• Dispose Pattern: Implement the IDisposable interface to release unmanaged resources.
• Finalizers: Use finalizers cautiously and implement the Dispose pattern for proper resource cleanup.
• Memory Profiling Tools: Utilize tools like dotMemory or Visual Studio Profiler to identify memory leaks and optimize resource usage.

9. Discuss the benefits and use cases of using ASP.NET Core middleware. Provide examples of scenarios where middleware can enhance the functionality of an application.

ASP.NET Core middleware components are used to handle requests and responses. Benefits include:

• Reusability: Middleware can be reused across different parts of the application.
• Pipeline Customization: Middleware allows customizing the request-response pipeline.

Examples of middleware scenarios include logging, authentication, and exception handling.

10. How does Entity Framework Core differ from Entity Framework 6? Discuss the key improvements and features introduced in Entity Framework Core.

Entity Framework Core (EF Core) is a lightweight, cross-platform version of Entity Framework (EF). Key differences and improvements include:

• Platform Independence: EF Core is designed to run on .NET Core, making it cross-platform.
• Performance: EF Core introduces better performance optimizations and reduced memory usage.
• No EDMX: EF Core eliminates the need for Entity Data Model XML (EDMX) files, simplifying the development process.

EF Core focuses on modern development practices and is suitable for a wide range of applications, including cloud-based and mobile applications.