Top C# Interview Questions for Experienced Professionals

Prepare for the most anticipated C# interview questions and answers for experienced professionals to increase your chances of landing a job at the top companies that use C# in their tech stacks, such as Accenture, Google, Delivery Hero, Wipro, Infosys, HCL, TCs, Microsoft, Stack Overflow, Intuit, and Trustpilot. 

C# is a programming language ideal for general purposes as it encompasses several disciplines such as object-oriented programming, component-oriented programming, and static and strong typing. C# is popularly used in the ASP.NET framework as it is ideal for creating web applications, websites, and games.

In this article, we present the most frequently asked C# interview questions and answers for experienced professionals.

C# Interview Questions and Answers for Experienced Professionals

The key concepts in the following list of C# interview questions for experienced professionals are explained simply and easily to help you ace your next job interview.

Q1. How is Exception Handling Implemented in C#?

You can carry out exception handling using the following four keywords in C#:

• try: A code block in which an exception is checked. 
• catch: This keyword catches an exception with the help of an exception handler
• finally: It is a code block written to execute irrespective of the exception being caught or not.
• throw: It throws an exception whenever a problem takes place.

Q2. How is Encapsulation Implemented in C#?

You can implement encapsulation by using access specifiers that define the scope and visibility of a class member. Some access specifiers are as follows:

• Public access specifier: It allows a class to expose its member functions and variables to other objects and functions. It allows access to any public member from outside the class.
• Private access specifier: It allows a class to hide its member functions and variables from other objects and functions. It allows only functions of the same class to access its private members.
• Protected access specifier: It allows a child class to access its base class's member function and variables, thus helping in inheritance implementation.

Q3. How is Overloading Different From Overriding?

Overloading and overriding are concepts in object-oriented programming that allow methods to be redefined or extended in a class. However, they differ in their purpose and implementation.

Aspect	Overloading	Overriding
Definition	Occurs when two or more methods in the same class have the same name but different parameters (type, number, or both).	Occurs when a subclass provides a specific implementation for a method defined in its superclass.
Purpose	Provides multiple ways to perform a similar action depending on different input parameters.	Allows a subclass to offer a specific implementation that differs from the superclass method.
Polymorphism Type	Compile-time polymorphism.	Runtime polymorphism through dynamic method dispatch.
Method Signatures	Involves different method signatures within the same class.	Involves the same method signature in both superclass and subclass.
Resolution	Resolved at compile-time.	Resolved at runtime.

These differences highlight the distinct roles that overloading and overriding play in enhancing the flexibility and functionality of object-oriented programming.

‍Q4. What do you Understand About Method Shadowing or Method Hiding in C#?

In C#, in method hiding, which is also known as method shadowing, the base class implementation of a method is hidden from the derived class through redefinition in the derived class. To make a method private, you can use the new keyword in the derived class. If you do not use the new keyword, the compiler will run the code, but it will put a warning. In method shadowing, the base class method is not marked as virtual and the derived class method does not use the new keyword.

Q5. What are Generics in C#.NET?

Generics promote the use of parameterized types, allowing you to write flexible and reusable code. With generics, you can create collection classes that work with any data type, ensuring type safety and reducing the need for casting.

In .NET, the System.Collections.Generic namespace is utilized to create generic collections instead of using non-generic classes. This approach improves performance and code clarity by specifying the type of objects the collection will hold, eliminating type mismatches, and enhancing maintainability. By leveraging generics, developers can create robust, type-safe collections, improving both the flexibility and efficiency of their code.

Q6. What do you Understand About Dependency Injection?

You can de-couple tightly linked classes using the dependency injection. Thus, it reduces the direct dependency of classes upon each other. You can achieve dependency injection via the following:

• Constructor dependency
• Property dependency
• Method dependency

‍

Q7. What do you Understand About Polymorphism in C#?

This is one of the most commonly asked C# interview questions and answers for experienced professionals. Polymorphism is one of the three main pillars of object-oriented programming after encapsulation and inheritance.

The term polymorphism means "many shapes." It occurs when there are many classes related to each other by inheritance.

For instance, at runtime, derived class objects may be treated as base class objects in places like collections/ method parameters/ arrays. In such polymorphism, declared and runtime types of objects are different. Thus, polymorphism allows a class to have multiple implementations with the same name.

Q8. Is it Possible to Serialize Hashtables?

No, you cannot serialize a hashtable in .NET. This is because the .NET Framework does not support the serialization of objects that implement the IDictionary interface, which includes Hashtable. As a result, attempting to serialize a hashtable will result in an error. For scenarios requiring serialization, consider using alternative data structures such as   Dictionary, which provides better serialization support in .NET.

Q9. What is Satellite Assembly?

A compiled library (DLL) containing localizable resources specific to a given culture like strings and bitmaps is referred to as a Satellite Assembly. You can use satellite assemblies while creating a multilingual UI application.

Q10. What is Interface Inheritance?

Interface inheritance is when a class inherits only the signatures of the functions from another class. It is also called type inheritance/ subtyping. It allows code reuse and polymorphism. The main advantage of interface inheritance is that it reduces coupling and implementation dependencies.

Q11. What are the Advantages of Using Partial Classes?

You can answer this C# interview question for experienced professionals by stating that the major advantages of using partial classes are

• They allow multiple developers to work on the same class easily.
• The code generators mainly use them to keep different concerns separate.
• It allows one developer to define the method while the other developer can implement it.

Q12.  What is String Interpolation in C#?

String Interpolation in C# allows you to create and format strings in a readable and convenient manner. By using the $ special character before a string, you can include expressions within curly braces {} that are dynamically evaluated and replaced with their string representations during runtime.

For Example: 

string name = "John";

int age = 30;

string message = $"Hello, my name is {name} and I am {age} years old."; 

In this example, the placeholders {name} and {age} are replaced with the values of the variables, resulting in a formatted string. String interpolation simplifies the process of formatting strings without needing complex concatenation or format methods.

Q13. What are Covariance and Contravariance in C#?

While covariance allows a method to have a return type, a subtype of the one defined in the delegate, contravariance allows a method to have a parameter type, i.e., a base type of the one defined in the delegate type.

Q14. What do Structs and Classes Have in Common, and How do they Differ?

You can answer this C# interview question for experienced professionals by stating that classes and structs have the following in common:

• They are compound data types.
• They can contain events and methods.
• They support interfaces

The key differences between structs and classes are as follows:

Point of Differences	Structs	Classes
Default access modifier	It is public in Structs	It is private
Memory allocation	They are generally allocated on the stack, meaning a copy is made when the struct is assigned to a new variable	They are reference types and thus are allocated on the heap. When a class is assigned to a new variable, a reference is assigned to the same object
Inheritance	It does not support inheritance	You can create a hierarchy of classes and reuse the code because classes support inheritance
Use cases	They are used for small and simple data structures with short lifetime	They are typically used for complex data structures that rely on inheritance
Performance	For small and short-term projects, they offer better performance	They are more efficient for large and long-term projects

Sample C# Interview Questions for Experienced Professionals

With these C# interview questions for experienced professionals, you can understand how well prepared you are for the technical interview. You can use these questions to practice and brush up on certain fundamental concepts.

1. What do you understand about boxing and unboxing?
2. Is it possible to store mixed data types such as string, int, float, and char in one array?
3. What is a race condition in C#?
4. How would you force Garbage Collection?
5. How is Lock different from Monitor in C#?
6. How is Var different from Dynamics in C#?
7. When would you use Tuples in C#?
8. How would you create a responsive UI without impacting users?
9. Why is the singleton pattern referred to as an anti-pattern?
10. How would you use Nullable Types in .NET?
11. How would you implement a singleton design pattern in C#?
12. What are the key differences between the "throw" and "throw ex" in .NET?

Coding C# Interview Question for Practice

You should be well-versed in data structures and algorithms to ace the coding C# interview questions in technical interview rounds.  

1. Write a program to reverse a string in C#.
2. How would you reverse the order of the given words in a string?
3. Write a program to find if the given string is palindrome or not.
4. Write a C# program to find if the given number is prime or not.
5. How would you count the occurrence of each character in a string?
6. Write a program to remove duplicate characters.
7. How would you perform the left circular rotation of a given array?

C# Interview Questions for Professionals with 3 Years Experience

With 3 years of experience, you are expected to have the basic, fundamental knowledge of C# concepts. You can use these questions to understand to gauge your preparedness.

1. How do you avoid deadlocks in multi-threaded C# applications?
2. What is the difference between directive and using statement in C#?
3. How does covariance and contravariance work in C#? Explain with an example.
4. Explain what is object pooling in C# and how it benefits multi-threaded programs.
5. How can you concatenate strings more efficiently in C# applications?
6. How is the yield keyword used to create iterators?
7. What is the difference between Memory and Span, and when should you use instead of the other?
8. How do you debug a memory leak in a C# application?
9. What is LINQ and how does it make data manipulation easier compared to working with regular loops?
10. How would you implement a custom serialization and deserialization of a class in C#?

C# Interview Questions for Professionals with 5 Years Experience

These C# interview questions cover important concepts and more advanced C# topics like method handling, memory management, and concurrency among others. Use these C# questions for professionals with 5 years experience to practice some of the more advanced concepts and topics.

1. Explain the difference between ref and out parameters in C#.
2. What do you mean by Boxing and Unboxing in C#?
3. What is the difference between Task vs Thread in C#?
4. Can you explain the difference between static class and singleton pattern in C#?
5. How do you create a custom exception in C#?
6. What's the purpose of the volatile keyword in C#?
7. How would you explain sealed and abstract classes?
8. What are extension methods in C# and how do you use them?
9. How would you compare and contrast async and await in C#?
10. How would you manage memory in C# so that memory leaks don't occur?
    

C# Interview Questions for Professionals with 10 Years Experience

If you are applying for senior C# developer roles, you should practice the following advanced C# interview questions to outperform the competition.

1. What do you understand about Reflection in C#? What are the common uses of Reflection?
2. What is an Assembly Manifest?
3. How would you generate a random number in C#?
4. How would you split a string using Regex in C#?
5. What is the use of app.config or web.config in C#?
6. What files get generated in the Debug folder when you create and compile an application in C#?
7. Is it possible to add extension methods to an existing static class?
8. What are the major differences between Object pooling and Connection pooling in C#?
9. What is the use of volatile keywords?
10. What is the role of the async method in C#?
11. How would you cancel an Async operation in C#?
12. State all the differences between Rectangular and Jagged Array in C#.

In addition to these C# interview questions for experienced professionals, you must practice mock interviews to nail the most challenging technical interviews.

Gear Up for Your Next Tech Interview

Preparing for technical interviews, especially the challenging ones, puts you on the path to becoming a better software professional with improved coding, problem-solving, and behavioral skills. You build more confidence for even the toughest interviews. 

At Interview Kickstart, we've trained thousands of coding engineers, software developers, and data scientists to land dream offers at the biggest companies, including Google, Facebook, Amazon, Apple, Microsoft, and Netflix. Check out some reviews to know more.

Sign up now for Backend Engineering Course at Interview Kickstart to uplevel your career!

FAQs: C# Interview Questions for Experienced Professionals

Q1. What Topics Should I Prepare for C# Interview Questions for Experienced Professionals?

You should thoroughly practice control statements, arrays, functions, object classes, properties, inheritance, abstraction, polymorphism, CLR, CLS, CTS, and strings exception handling to ace C# interview questions and answers for experienced professionals.

Q2. How Should I Prepare for C# Interview Questions and Answers for Experienced Professionals?

You must get well-versed in basic and advanced concepts of C#. Practice the most anticipated interview questions, and practice mock interviews. You must practice multiple coding problems to improve your speed and accuracy.

Q3. What are the Main Differences Between C and C#?

The key difference between C and C# is that the C language can be executed cross-platform, whereas the .NET framework is required to execute the C# language. In the C language, garbage collection is not available, but C# features garbage collection managed by Common Language Runtime (CLR).

Q4. Which Companies Use C# Interview Questions and Answers for Experienced Professionals?

Several top companies use C# interview questions and answers for experienced professionals, including Google, Wipro, Infosys, Accenture, JP Morgan, HCL, TCS, and Google.

Q5. What is the Average Salary of a C# Developer in the US?

The salaries of C# developers range from $60,000 to $160,000 in the United States, and the average salary is $80,000 (Source: comparably.com).

‍Related reads:

• How to Solve Bit Manipulation Interview Questions: Bit Manipulation Essentials for Embedded Software Engineers
• Top Technical Program Manager Interview Questions For Meta
• Top Software Engineer Interview Questions For Mongodb
• Top 25 Advanced C++ MCQs for Experienced Programmers
• 35 Essential Artificial Intelligence MCQs for Interview Preparation