C# Interview Questions and Answers (2025)

C# is a powerful, object-oriented programming language used in web development, desktop applications, and enterprise solutions. Below is a list of 20 interview questions categorized into behavioral, situational, technical, and cultural fit types, with concise answers reflecting industry best practices.

1. Behavioral Questions

• Q1: Can you describe a challenging C# project you worked on?
  A: I developed a multi-threaded application that optimized database queries, reducing response time by 40%.
• Q2: Have you ever had to debug a complex C# application?
  A: Yes, I used Visual Studio's debugging tools and logs to trace memory leaks in a large-scale application.
• Q3: How do you stay updated with C# advancements?
  A: I follow Microsoft documentation, attend webinars, and experiment with new .NET features.
• Q4: Describe a time when you optimized C# code.
  A: I refactored a LINQ query, reducing execution time by 30% and improving maintainability.
• Q5: How do you handle tight deadlines in C# projects?
  A: I prioritize tasks, break them into smaller milestones, and use Agile methodologies.

2. Situational Questions

• Q6: What would you do if you encountered a performance bottleneck in a C# application?
  A: I would profile the application using tools like dotTrace and optimize inefficient code sections.
• Q7: How would you handle a memory leak in a C# application?
  A: I would use memory profilers and analyze garbage collection patterns to find and fix leaks.
• Q8: If a junior developer writes inefficient C# code, how would you approach them?
  A: I would explain best practices, show alternative solutions, and encourage collaborative debugging.
• Q9: What would you do if a client requested a last-minute feature in a C# project?
  A: I would assess feasibility, communicate realistic timelines, and implement the change efficiently.
• Q10: How do you ensure security in a C# web application?
  A: I implement input validation, encrypt sensitive data, and use authentication frameworks like IdentityServer.

3. Technical Questions

• Q11: What is the difference between struct and class in C#?
  A: Structs are value types stored on the stack, whereas classes are reference types stored on the heap.
• Q12: What are async and await in C#?
  A: They enable asynchronous programming by allowing non-blocking execution of tasks.
• Q13: What is dependency injection in C#?
  A: It’s a design pattern that provides dependencies to a class rather than hardcoding them.
• Q14: What is a lambda expression in C#?
  A: It is an anonymous function that can contain expressions or statements used in LINQ queries.
• Q15: How do you handle exceptions in C#?
  A: By using try-catch blocks and logging errors with frameworks like Serilog or NLog.

4. Cultural Fit Questions

• Q16: How do you collaborate with cross-functional teams?
  A: By maintaining clear communication, using Agile tools, and participating in team discussions.
• Q17: What values do you think are important in a C# development team?
  A: Teamwork, code quality, continuous learning, and accountability.
• Q18: How do you handle constructive feedback?
  A: I welcome feedback, use it to improve, and apply suggestions in future work.
• Q19: Why do you want to work with our company?
  A: Your company’s innovation and emphasis on technology-driven solutions align with my expertise.
• Q20: How do you manage work-life balance while working on critical projects?
  A: By prioritizing tasks, setting boundaries, and maintaining an organized schedule.

More Technical Questions

• Q21-Q50 cover topics like generics, multithreading, SOLID principles, design patterns, LINQ, and ASP.NET Core.