Top 10 Senior C# Developer Interview Questions & Answers in 2024

1. Explain the principles of SOLID and how they apply to C# development.

SOLID is an acronym for five design principles: Single Responsibility, Open/Closed, Liskov Substitution, Interface Segregation, and Dependency Inversion. These principles guide developers in creating maintainable and scalable software. For example, Single Responsibility Principle (SRP) suggests that a class should have only one reason to change, promoting modularity and easier maintenance.

2. Discuss the use of 'yield' in C# and provide an example of its application.

The 'yield' keyword in C# is used to create iterators or generators. It allows the implementation of custom iteration logic without creating a full collection in memory. For instance, using 'yield return' in a method generates elements one at a time, making it memory-efficient for large datasets.

3. Explore the differences between 'readonly' and 'const' in C#.

'const' is a compile-time constant, and its value must be known at compile time. 'readonly' is a runtime constant, and its value can be assigned at runtime but remains constant thereafter. 'const' is often used for mathematical constants, while 'readonly' is suitable for values determined at runtime.

4. Describe the benefits and drawbacks of using Dependency Injection (DI) in C#.

Dependency Injection improves code maintainability, testability, and modularity by injecting dependencies rather than creating them internally. However, it adds complexity and can be overused, leading to excessive configuration. DI frameworks like Microsoft.Extensions.DependencyInjection simplify the implementation of DI in C#.

5. Explain the concept of 'async/await' in C# and its impact on application performance.

'async/await' enables asynchronous programming in C#, allowing non-blocking execution of code. While it improves responsiveness, it doesn't necessarily improve raw performance. Asynchronous code may have an overhead due to context switching. Developers should carefully balance the use of 'async/await' based on the application's requirements.

6. Discuss the role of the 'using' statement in C# and its impact on resource management.

The 'using' statement in C# is primarily used for resource management, ensuring that IDisposable objects are properly disposed when they go out of scope. It reduces memory leaks and enhances code readability. 'using' is commonly employed with database connections, file streams, and other resource-intensive objects.

7. Explore the features and use cases of the 'Span' and 'Memory' types in C#.

'Span' and 'Memory' types are introduced in C# for efficient memory handling. 'Span' represents a contiguous region of arbitrary memory and is often used in scenarios like string manipulation. 'Memory' is a read-only representation of 'Span' and is suitable for scenarios where data should not be modified.

8. Explain the purpose of the 'Lazy' class in C# and provide an example of its usage.

'Lazy' is a class in C# that defers the creation of an object until it is accessed. This can be useful for optimizing resource-intensive operations. For instance, creating a 'Lazy' instance for a complex calculation ensures that the calculation is performed only when the value is first requested.

9. Discuss the use of Attributes in C# and provide an example where custom attributes can be beneficial.

Attributes in C# provide metadata that can be added to code elements. Custom attributes are user-defined metadata. For example, creating a custom attribute to mark methods that should be logged allows developers to annotate methods with additional information, improving code documentation and maintainability.

10. Explain the differences between 'lock' and 'Monitor' in C# for synchronization purposes.

'lock' and 'Monitor' are both used for synchronization in multithreaded applications. 'lock' is a shorthand for 'Monitor.Enter' and 'Monitor.Exit', providing a convenient way to synchronize code blocks. 'Monitor' provides more granular control, allowing developers to wait for a specific signal. Choosing between them depends on the specific synchronization needs of the application.