Most Frequently Asked C# Interview Questions

Most Frequently Asked C# Interview Questions 

 Are you preparing for your C# Interview? Here you can find the Top C# Interview Questions. The Most Common C# Interview Questions list for both freshers and experienced includes basics of OOPS, C# Fundamentals, .Net Fundamentals, C# Data Types, Multithreading, Tasks,  Delegate, Async Programming,  LINQ, C# Operators, SOLID Principles, Reflection,  etc.  

Please visit my YouTube Channel for more C# Interview Questions and Answers videos by the below link:

Watch C# Interview Questions and Answers videos here.

Below are the Most Frequently Asked C# Interview Questions list for both freshers and experienced:

Q001. What are the 4 pillars of OOPS (Object-Oriented Programming Language)?

Q002. What is the difference between Abstraction and Encapsulation?

Q003. What is the difference between Class and Structure in C#?

Please read the C# Structure article here.

Q004. What are the different Access Modifiers in C#?

Q005. What is Polymorphism in C#? What are the different types of Polymorphism?

Q006. What are the different ways to implement Polymorphism in C#?

Please read the Run Time Polymorphism implementation article here. Please watch the Run Time Polymorphism implementation video here.

Q007. What is the difference between Early Binding and Late Binding in C#? or What is the difference between Static Binding and Dynamic Binding in C#?

Please read the Late Binding or Dynamic Binding article here. Also please watch the Late Binding or Dynamic Binding video here.

Q008. What is Shadowing in C#?

Please read the Shadowing article here. Please watch the Shadowing video here.

Q009. What is the Method Hiding in C#? How can you achieve that?

Please read the Hiding article here. Please watch the Hiding video here.

Q010. What is the abstract method? How an abstract method is different from the virtual method?

Please read the Abstract Method article here. Please watch the Abstract Method video here.

Q011. What is the difference between Overloading and Overriding in C#?

Q012. Can you achieve method overloading by inheritance? How?

Q013. Can we overload the main() method in C#?

Q014. Can you achieve method overriding without inheritance? How?

Q015. What is the difference between Method Overriding and Method Hiding?

Please read the Method Overriding vs Method Hiding article here. Please watch the Method Overriding vs Method Hiding video here.

Q016. We have two methods, one is returning IEnumerable results and the second one is void. Is it an example of Static Polymorphism?

Q017. What is Constructor Overloading in C#? Can you overload a static constructor in C#?

Please read the Constructor and Constructor Overloading article here. Please watch the Constructor Overloading video here.

Please read the Static Class and Static Constructor article here. Please watch the Static Constructor video here.

Q018. What is the difference between a virtual method and an abstract method?

Please read the Abstract Method vs Virtual Method article here. Please watch the Abstract Method vs Virtual Method video here.

Q019. What is the difference between inheritance and composition? Why Composition is immune to Fragile Base Class Problem?

Please watch the Inheritance vs Composition video here.

Q020. How can you achieve composition with the abstract classes? 

Q021. What happens if the inherited interfaces have conflicting method names? or What is explicit interface implementation?

Please watch the Interface Implementation Having Duplicate Methods video here.

Q022. What is the Fragile Base Class Problem (FBCP) of OOPS? How can you avoid this problem? 

Please watch the Fragile Base Class Problem video here. Please watch how the .Net Framework handles the Fragile Base Class Problem here.

Q023. What is an abstract class? Can an abstract class implement an interface?

Please read the Abstract Class article here. Please watch the Abstract Class video here.

Q024. When do you choose interface over an abstract class or vice versa?

Q025. Can you define constructors in the abstract class? What is the use of a constructor in an abstract class that can not be instantiated?

Q026. Can you create the object of the abstract class? Is it mandatory to have abstract members in the abstract class?

Please read the Abstract Class Fundamentals Rules article here. Please watch the Abstract Class video here.

Q027. What is the difference between abstract class and interface?

Please read the Abstract Class vs Interface article here. Please also watch the Abstract Class vs Interface video here.

Q028. Does C# support multiple inheritances? Why?

Please read the Multiple Inheritance article here. Please also watch the C# Multiple Inheritance video here.

Q029. What is the Diamond Problem in C#?

Please read the Diamond Problem article here. Please also watch the Diamond Problem video here.

Q030. What is the difference between class inheritance and interface inheritance in C#?

Q031. What is the difference between multiple and multilevel inheritances?

Q032. What is the order of constructor execution in the case of inheritance?

Please watch the Constructor Execution Sequence Order video here.

Please read the C# Constructor article here. You can also watch the Instance Constructor video here.

Q033. What is the order of static constructor execution in the case of inheritance?

Please watch the Constructor Execution Sequence Order video here.

Please read the C# Static Constructor article here. Please also watch the C# Static Constructor video here.

Q034. Can two classes having different accessibility be inherited?

Q035. What is the static class? Can a static class implement interface, why?

Please read the C# Static Class article here. Please also watch the C# Static Class video here.

Please read the C# Static Class Interview Questions and Answers article here. Please also watch the C# Static Class Interview Questions and Answers video here.

Q036. What is the difference between a static class and an instance class having all members as static?

Q037. Can you inherit a class in a structure in C#?  Why?

Q038. What is the difference between structure and class in C#?

Please read the C# Structure vs Class article here. 

Q039. Can you define a destructor in a structure? Why?

Q040. Can a structure have protected members? Why?

Q041. What is the difference between static class and instance class?

Please read the C# Static Class vs Instance Class article here. Please also watch the C# Static Class video here.

Q042. What is the difference between static class and singleton?

Q043. What is the use of static class? Can you give me some real examples of static class and static methods available in .Net?

Please read the C# Static Class Real Use article here. Please also watch the C# Static Class Real Use video here.

Q044. What is a partial class in C#? What is the use of partial class, do you have any real examples?

Please read the C# Partial Class article here. Please also watch the C# Partial Class video here.

Q045. What is a partial method in C#? What is the use of partial methods?

Please read the C# Partial Method article here. Please also watch the C# Partial Method video here.

Q046. Can you give me some real examples of partial classes and partial methods available in the .Net?

Please read the C# Partial Class Real Examples article here. Please also watch the C# Partial Class Real Examples video here.

Q047. What is the difference between string and String or int and Int32 in C#?

Please watch the string vs String video here.

Q048. What is the difference between String and StringBuilder in C#?

Please watch the String vs StringBuilder video here.

Q049. What do you understand by the term 'Typesafe'? Is C# a typesafe language?

Q050. What are Tuples in C#? What is the main use of it?

Q051. What are the differences between value types and reference types?

Q052. What are the differences between reference types and pass-by-reference?

Please watch the Reference Type vs Pass By Reference video here.

Q053. What are the differences between OUT and REF types parameters?

Please watch the OUT vs REF video here.

Q054. Can you pass a constant as a reference? Why?

Please watch the Const vs Readonly video here.

Q055. If a method’s return type is void, can you use a return statement in the method?

Q056. What is the recursive method? Can you tell me any available recursive method names in c#?

Q057. In C# strings are the value type or reference type? Why?

Q058. Enums are value type or a reference type in C#? Why?

Q059. In C# structure is a value type or a reference type? Why?

Please read the C# Structure article here. 

Q060. What is the difference between casting and conversion in C#?

Please watch the Conversion vs. Casting video here.

Q061. What is the difference between boxing and unboxing in C#?

Please watch the Boxing vs Unboxing video here.

Q062. What is the difference between boxing and conversion in C#?

Q063. What is the difference between unboxing and casting?

Q064. What is the difference between int.Parse() and int.TryParse() methods?

Q065. What is the difference between .ToString() and Convert.ToString() in C#?

Please watch the ToString vs Convert.ToString video here.

Q066. What is the difference between String.IsNullOrEmpty() and String.IsNullOrWhiteSpace() in C#?

Please watch the String.IsNullOrEmpty vs String.IsNullOrWhiteSpace video here.

Q067. What is a sealed class in C#? Can you make the abstract class sealed?

Please read the C# Sealed Class article here. Please also watch the C# Sealed Class video here.

Q068. What is the sealed method in C#? How can you make any method sealed?

Please read the C# Sealed Method article here. Please also watch the C# Sealed Method video here.

Q069. What is the difference between the sealed method and the private method in C#?

Please read about the C# Sealed Method vs Private Method article here. Please also watch the C# Sealed Method vs Private Method video here.

Q070. What is the difference between Sealed Class and Abstract Class in C#?

Please read about the C# Sealed Class vs Abstract Class article here. Please also watch the C# Sealed Class vs Abstract Class video here.

Q071. What is the difference between Sealed Class and Static Class in C#?

Please read about the C# Sealed Class vs Static Class article here. Please also watch the C# Sealed Class vs Static Class video here.

Q072. How a sealed class is different from a class having a private constructor in C#?

Please read the answer to this question and also more C# Sealed Class Interview Questions and Answers in this article here. 

Please also watch the C# Sealed Class Interview Questions and Answers video here.

Q073. What is a destructor, how does it affects the garbage collection process? When should we define destructor in C#?

Please read about the C# Destructor article here. 

Q074. When the destructor is called? Can you pass parameters to destructors? How many destructors can be defined in any class?

Q075. What is garbage collection in C#? What are the different generations of GC?

Q076. What is the difference between destructor and Finalizer in C#?

Q077. What is the difference between IDisposable and Finalizer? or What is the difference between dispose and finalize method in C#?

Please read about the C# IDisposable Interface article here. 

Q078. Can a static class have a destructor? Why?

Q079. What is the use of the using statement or using block in C#?

Please read about the C# Using Statement Dispose Pattern article here. 

Q080. What is recursion? Which data structure is used by the recursion, stack, or queue?

Q081. What is a delegate in C#? Can you tell me some most common delegates available in C#?

Q082. What are the FUNC and PREDICATE delegates in C#?

Q083. What is the difference between System.Collections and System.Collections.Generic namespaces?

Q084. What is the difference between an Array and ArrayList() in C#?

Q085. What’s the difference between the Array.CopyTo() and Array.Clone()?

Q086. What is the difference between constant and readonly in C#?

Please watch the C# Const vs Readonly video here. 

Q087. What is an indexer in C#? Can you define the indexer in the static class, why?

Q088. Can a try block exist without catch block in C#?

Please watch the C# Try-Catch Blocks video here. Please also watch the C# Finally Blocks video here. 

Q089. What is the difference between debug and release mode?

Please watch the C# Debug vs Release Mode video here. 

Q090. What is the use Checked and Unchecked keyword in C#?

Q091. What is the difference between IEnumerable and IEnumerator in C#?

Q092. What is the difference between IEnumerable and IQueryable in C#?

Q093. What is the difference between IEnumerable and List in C#?

Q094. What is the use of Params keyword in C#?

Q095. What is Data Annotation in C#? How can you do remote validation using it?

Q096. What is the difference between Equality Operator "==" and .Equals() method comparison in C#?

Please watch the "==" vs .Equals video here. 

Q097. What is a private constructor? What is the use of a private constructor?

Please watch the C# Private Constructor video here. 

Q098. What is a static constructor in C#? How can you call the static constructor?

Please watch the C# Static Constructor video here. 

Q099. What is the Constructor Chaining in C#? How it is different from Constructor Overloading?

Please watch the C# Constructor Chaining video here. 

Q100. What are the generics in C#? How can you define a generic class and methods in C#?

Q101. Can you prevent a class from being instantiated? How?

Please visit the C# Sealed Class Interview Questions and Answers article here. 

Q102. What is reflection? What is the use of reflection in C#?

Q103. What is LINQ in C#?

Q104. What are Anonymous Types in C#? How it is different from dynamic types?

Q105. What happens if the finally block throws an exception?

Please watch the C# Finally Block Exception video here. 

Q106. What is finally block? How many finally blocks can you define with a try block?

Q107. What is the difference between final, finally, and finalize?

Q108. What is the difference between the “throw” and “throw ex” in .NET?

Please watch the C# Throw vs Throw ex video here. 

Q109. What is the difference between the IS and AS Operators in C#?

Please watch the IS vs. AS video here. 

Q110. What is the difference between foreach and for loop in C#?

Q111. What is the difference between ForEach and Parallel.ForEach loop in C#?

Q112. What is the difference between Process and Thread?

Q113. What is Multithreading and why do we need Multithreading in our project?

Q114. What is the difference between task and thread?

Q115. What is the difference between monitor and lock in C#?

Q116. What is deadlock? What are the four necessary conditions for Deadlock?

Q117. What is the volatile keyword? What is the use of volatile keyword in C#?

Q118. What is the Semaphore?

Q119. What is Mutex and how it is different from other Synchronization mechanisms?

Q120. How can you share data between multiple threads?

Q121. What is synchronization and why it is important?

Q122. What is Dependency Injection? What problems does the dependency injection solve?

Q123. What is Inversion of Control?

Q124. What are SOLID Principles? Why do we need it?

Q125. What is the difference between managed and unmanaged code?

Q126. How do you manage the exceptions or application logs in your project?

Q127. What is the difference between task.delay() and thread.sleep() in C#?

Q128. What are extension methods in C#? How can you create extension methods in C#?

Q129. What is the exact difference between deferred execution and lazy execution in C#?

Q130. What is the use of async and await in C#? How does it work?

Q131. What is the difference between this and base in C#?

Please watch the C# Constructor Chaining video here. 

Q132. What is the difference between First() and FirstOrDefualt() in C#?

Q133. What is the difference between EXE and DLL in .Net?

Q134. What is the difference between assembly and namespace in .Net?

Q134. What is the app domain or application domain in .Net? How it is different from App Pool?

Q135. What is the difference between project rebuild and project clean and build in C#?

Q136. What is the difference between instance field and property in the C# class?

Please watch the C# Fields vs Property video here. 

Q137. What is the difference between the C# 7 Interface and C# 8 Interface?

Please read the New Features of the C# 8 Interface here. Please watch the New Features of the C# 8 Interface video here. 

Q138. What is Circular Dependency and how can you resolve this issue?

Q139. What is DLL Hell Problem and how can you resolve this issue?

Q140. What is TPL (Task Parallel Library) in the .Net?

Q141. What is the difference between Concurrency and Parallelism?

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