Top 100 C# interview questions to assess candidates for developer positions

Given the significant number of professionals proficient in C#, it is crucial to implement a robust recruitment process that effectively evaluates the skills and expertise of applicants. This process ensures the selection of candidates who are best suited for the job role and align with the organization’s requirements.

It is essential to conduct comprehensive interviews to assess candidates’ technical skills and ensure their suitability according to an organization’s requirements. This can be achieved with C# interview questions that focus on their expertise in software engineering, programming knowledge, and experience in software development.

Designing a customized and robust recruitment process, including C# interview questions, ensures quality hiring. Here are some commonly asked C# interview questions and answers across the basic, intermediate, and advanced levels that candidates should know.

Forty-three basic C# interview questions

1. What is C#?
2. Why was C# invented?
3. What are the advantages of using C#?
4. What types of comments are there in C#?
5. Name some of the IDEs Microsoft provided for C# development.
6. What does CLR stand for?
7. For a single exception in a C# program, is it possible to execute multiple catch blocks?
8. What is the difference between C and C#?
9. Is CLR the equivalent of .Net?
10. What is the full form of SOAP?
11. Explain common language runtime.
12. Define indexers.
13. What types of classes are there in C#?
14. Are multiple inheritances supported in C#?
15. Are C++ and C# the same?
16. What is the extension of C# language files?
17. Which symbols mark the start and end of a code block?
18. What are operators?
19. Is C# a type-safe language?
20. How to get the array index using a ‘for each’ loop?
21. Which keyword is used to come out of a loop?
22. Can a class be inherited into another class?
23. Is it possible to override a function in the same class?
24. What are subroutines called in C#?
25. List some members of namespaces in C#.
26. Can private virtual methods be overridden?
27. Which symbol is used in C# to terminate a statement?
28. Is C# a case-sensitive language?
29. Can a ‘this’ command be used within static methods?
30. Which symbol marks the beginning of a single-line comment in C#?
31. Which symbols are used for multi-line comments?
32. Which statement is used to declare variables in C#?
33. Which data type is used to store text values?
34. Which syntax is used to define constants?
35. What is a console in C#?
36. Can the foreach loop be used in C#?
37. What are throw statements in C#?
38. Which class is the UInt data type derived from in C#?
39. Which access specifier is used for the Main () method in C#?
40. Why is the C# pointer used?
41. Which symbol is used to access fields or variables inside a class?
42. What are the variables in C#?
43. How is exception handling done in C#?

Five of the basic C# interview questions and their answers

1. Why was C# invented?

Candidates should be aware that C# was developed in 2000 by Microsoft to meet the rising demands for web applications.

2. What are the advantages of using C#?

Some advantages candidates may list are:

• The language is easy to learn and highly scalable.
• C# has fast development times, and can be compiled on multiple computer platforms.
• C# is modular, allowing developers to work on multiple objects simultaneously and making troubleshooting easier.

3. What is the difference between C and C#?

The candidates’ answers may vary, but they should have the basic knowledge that C supports procedural programming while C# supports object-oriented programming.

4. Explain common language runtime.

Candidates should be able to explain that common language runtime (CLR) is a virtual machine component of the .NET framework that manages code executions of .NET programs.

5. Are C++ and C# the same?

No. C++ is a low-level programming language than C#. Additionally, C++ compiles to machine code, whereas C# compiles to CLR.

Twenty-eight intermediate C# interview questions

1. What is recursion in C#?
2. What are multicasting delegates?
3. What are namespaces?
4. What are the steps of code compilation in C#?
5. Name some of the access modifiers available in C#.
6. Which parameter returns multiple values from a function?
7. What is an abstract class in C#?
8. What is the default interface method?
9. What is polymorphism?
10. What role do the access modifiers in C# play?
11. What are the types of constructors in C#?
12. Give the syntax used to declare an object of the class.
13. Which symbol is used to define variable types when declaring arrays?
14. What is string length?
15. Which string class operator decides if two given strings have different values?
16. Differentiate between object type and dynamic type variables.
17. What are the different ways of passing parameters to methods?
18. How can an infinite loop be run using the for () statement?
19. What are the data types present in C#?
20. What are keywords in C#?
21. Define jagged arrays.
22. What is a local variable in C#?
23. What is inheritance in C#?
24. Why are multiple inheritances not supported in C#?
25. Which keyword can be used to implement duck typing?
26. What are read-only variables?
27. Can the value of a variable be changed while debugging the application?
28. What is LINQ?

Five of the intermediate C# interview questions and their answers

1. What is recursion in C#?

Recursion in C# refers to the process of making a function call itself.

2. What are the steps of code compilation in C#?

There are four steps of code compilation:

• Pre-processing
• Compiling
• Assembling
• Linking

3. What is string length?

It is used to get the count of characters in a string.

4. What are the data types present in C#?

Candidates should know that there are four data types in C#: Char, Int, Float, and Double.

5. What is a local variable in C#?

Local variables are variables that are defined in a code block. These variables are only visible in the code block in which they have been declared.

Twenty-nine advanced C# interview questions

1. What are constructors?
2. What is the difference between read-only and const?
3. Define method overloading.
4. Give the features of a read-only variable.
5. What are dynamic type variables?
6. What is a ‘using’ statement?
7. What are nullable types?
8. What are the stream reader and stream writer classes?
9. What is the difference between overriding and overloading?
10. What is file handling in C#?
11. What are boxing and unboxing?
12. Highlight the key differences in unmanaged and managed code?
13. What is the difference between structure and class?
14. Differentiate between task and thread.
15. How is encapsulation done?
16. What are destructors, and when are they used?
17. Why can the accessibility modifier not be specified for methods inside the interface?
18. What is the difference between the keywords ref and out?
19. When is the finally block used?
20. Write a C# program that would help reverse a string.
21. Write a C# program to reverse the order of words given.
22. Write a C# program to find if a given string is a palindrome.
23. Write a C# program to find a substring from a given string.
24. Write a program for removing duplicate characters in a string.
25. Write a program to find the sum of the digits in a positive integer.
26. Write a program to check if an entered number is not divisible by 77 and 3.
27. What are the get and set accessor properties?
28. What is the use of async and await in C#?
29. What are extension methods in C#?

Five of the intermediate C# programming interview questions and their answers

1. What are constructors?

Constructors are methods executed when new class objects, public or private, are created.

2. What is the difference between a read-only and a const?

Read-only are runtime constants, while const are compile-time constants.

3. What is a ‘using’ statement?

The ‘using’ statements in C# ensure that objects are disposed of as soon as they go out of scope, without the need to write any code.

4. What are the stream reader and stream writer classes?

Both stream reader and stream writer classes are inherited from the abstract base class stream and are used for writing and reading actions to a file.

5. Why can the accessibility modifier not be specified for methods inside the interface?

In an interface, there are no method definitions for virtual methods. The methods are written to be overridden in the derived class and are publicly available.

Scenario-based C# programming interview questions are designed to help assess candidates’ problem-solving and decision-making skills in specific situations. These questions encourage candidates to demonstrate their ability to communicate effectively, think critically, and provide practical solutions to real-world problems.

Examples of scenario-based C# interview questions for a senior developer

1. How to create multi-threaded applications in C#? Give 2-3 examples.
2. How to create a multi-threaded application without explicitly creating a thread?
3. What methods help create re-entrant code?
4. How to create a responsive UI without using threads?
5. How to explain monads to a non-programmer?

Including basic C# interview questions, advanced C# interview questions for senior developers, and scenario-based C# interview questions for experienced professionals is a great way to get insights into the candidates’ skills. However, these interview questions can only comprise part of the candidate assessment process. Additional tests, like job-specific skills, soft skills, and personality tests, should also be included in the recruitment process to make well-informed hiring decisions free from bias.

Interview questions should ideally be scheduled after administering a basic skills test to screen initial applicants. Using the right C# interview questions, hiring managers can delve deep into the coding credentials of candidates toward the end of the selection process. The earlier stages of recruitment should identify the best candidates from the pool of applicants, who can then be evaluated thoroughly for technical expertise.

Candidates for C# developer roles can be evaluated using role-based tests and tasks to ascertain their expertise in the language. It is important to ensure that the skills assessment and the C# interview questions are tailored to the specific requirements of the job role in question.

It is necessary to go beyond the basic assessments and interview questions to find qualified C# developers for an open position. Tailor C# interview questions to ensure that they challenge candidates and are enough to provide insights into the knowledge and skills of candidates.

With the right C# interview questions and the scientifically validated assessments by Mercer | Mettl, hiring managers can assess applicants objectively and without bias.

To fully leverage the capabilities of C# and its digital systems, organizations must have access to competent C# developers. Hiring such skilled professionals necessitates the implementation of a comprehensive recruitment process that includes multiple stages. This process should incorporate skills assessments, coding simulations, and rounds of C# interview questions and answers. By employing these measures, organizations can identify and select developers who possess the necessary expertise and proficiency in C#, ensuring the successful utilization of the language and its associated technologies.