.NET / C# Interview Questions with Answers.

If you are looking to clear C# and .NET Interviews then you have landed at the right course. You can be a hero in your project/company , you must have handled complex scenarios.

But failing to answer simple .NET , C# Fundamental question during interview can lead to a very negative impact during interviews.

This course focuses on Fundamental questions around C# and .NET... Happy job hunting.

Below is the list of C# interview questions covered in the Series.

Part 1 - Stack, Heap, Boxing, Unboxing, Array, ArrayList, Generics, ThreadingQuestion 1 :- Explain difference between .NET and C# ? Question 2 :- .NET Framework vs .NET Core vs .NET 5.0 Question 3 :- What is IL ( Intermediate Language) Code ? Question 4 :- What is the use of JIT ( Just in time compiler) ? Question 5 :- Is it possible to view IL code ? Question 6 :- What is the benefit of compiling in to IL code ? Question 7 :- Does .NET support multiple programming languages ? Question 8 :- What is CLR ( Common Language Runtime) ? Question 9 :- What is managed and unmanaged code ? Question 10 :- Explain the importance of Garbage collector ? Question 11 :- Can garbage collector claim unmanaged objects ? Question 12 :- What is the importance of CTS ? Question 13 :- Explain CLS ? Question 14 :- Difference between Stack vs Heap ? Question 15 :- What are Value types & Reference types? Question 16 :- Explain boxing and unboxing ? Question 17 :- What is consequence of boxing and unboxing ? Question 18 :- Explain casting, implicit casting and explicit casting ? Question 19 :- What can happen during explicit casting ? Question 20 :- Differentiate between Array and ArrayList ? Question 21 :- Whose performance is better array or arraylist ? Question 22 :- What are generic collections ? Question 23 :- What are threads (Multithreading)? Question 24 :- How are threads different from TPL ? Question 25 :- How do we handle exceptions in C#(try/catch)? Question 26 :- What is the need of finally? Question 27 :- Why do we need the out keyword ? Question 28 :- What is the need of Delegates ? Question 29 :- What are events ? Question 30 :- What's the difference between Abstract class and interface ?

Part 2 - Questions on Delegates, Event and Delegates vs Events.Question 31  :- What is a delegate and How to create a delegate ?Question 32  :- Where have you used delegates ?Question 33  :- What is a Multicast delegates ?Question 34  :- What is a Event ?Question 35  :- How to create a event ?Question 36  :- Delegate vs Events.

Part 3 - OOP, Abstraction, Encapsulation, Inheritance, Overriding & overloading.Question 37 :- Why do we need OOP ?Question 38 :- What are the important pillars of OOPs ?Question 39 :- What is a class and object ?Question 40 :- Abstraction vs Encapsulation?Question 41 :- Explain Inheritance ?Question 42 :- Explain virtual keyword ?Question 43 :- What is overriding ?Question 44 :- Explain overloading ?Question 45 :- Overloading vs Overriding ?

Part 4 - Polymorphism, Static vs Dynamic polymorphism and operator overloading.Question 46 :- What is polymorphism ?Question 47 :- Can polymorphism work with out inheritance ?Question 48 :- Explain static vs dynamic polymorphism ?Question 49 :- Explain operator overloading ?

Part 5 - Tricky Questions around Abstract classes and Interfaces.Question 50  :- Why do we need Abstract classes ?Question 51  :- Are Abstract methods virtual ?Question 52  :- Can we create a instance of Abstract classes ?Question 53  :- Is it compulsory to implement Abstract methods ?Question 54  :- Why simple base class replace Abstract class ?Question 55  :- Explain interfaces and why do we need it ?Question 56  :- Can we write logic in interface ?Question 57  :- Can we define methods as private in interface ?Question 58  :- If i want to change interface what's the best practice ?Question 59  :- Explain Multiple inheritance in Interface ?Question 60  :- Explain Interface Segregation principle ?Question 61  :- Can we create instance of interface ?Question 62  :- Can we do Multiple inheritance with Abstract classes ?

Part 6 - Answering the most asked Question "Abstract classes vs Interface".Question 63 :- Difference between Abstract Class & Interfaces?

Part 7 - Questions around constructors & parent child constructor.Question 64  :- Why do we need constructors ?Question 65  :- In parent child which constructor fires first ?Question 66  :- How are initializers executed ?Question 67  :- How are static constructors executed in Parent child ?Question 68  :- When does static constructor fires ?

Part 8 - Questions around Shadowing, Sealed, Nested classes and partial classes.Question 69 :- What is Shadowing?Question 70 :- Explain method hiding?Question 71 :- Shadowing vs Overriding ?Question 72 :- When do we need Shadowing ?Question 73 :- Explain Sealed Classes ?Question 74 :- Can we create instance of sealed classes ?Question 75 :- What are nested classes and when to use them ?Question 76 :- Can Nested class access outer class variables ?Question 77 :- Can we have public, protected access modifiers in nested class ?Question 78 :- Explain Partial classes ?Question 79 :- In What scenarios do we use partial classes ?

Part 9 - Questions Around SOLID principles , Dependency injection (DI) and IOCQuestion 80 :- What is SOLID ?Question 81 :- What is the full form of SOLID ?Question 82 :- What is the goal of SOLID ?Question 83 :- Explain SRP with A example ?Question 84 :- What is the benefit of SRP ?Question 85 :- Explain OCP with a example ?Question 86 :- What is the  benefit of OCP ?Question 87 :- Can you explain LISKOV Principle and it's violation?Question 88 :- How can we fix LISKOV Problem ?Question 89 :- Explain Interface Segregation Principle ?Question 90:- Is there a connection between LISKOV and ISP ?Question 91 :- Define dependency inversion ?Question 92 :- What is higher level module and lower level module ?Question 93 :- How does dependency inversion benefit, show with an example ?Question 94 :- Will only Dependency inversion solve decoupling problem ?Question 95 :- Why do developers  move object creation outside high lever module ?Question 96 :- Explain IOC ( Inversion of Control) ?Question 97 :- Explain Dependency Injection with an example ?Question 98 :- IsQuestion 99 :- Is only SOLID Enough for good code/ architecture ?

Part 10- Explain & Differentiate Composition, Aggregation and Association in C#.Question 100 :- What are the different types of "USING/HAS A" relationship ?Question 101 :- What is a composition relationship ?Question 102 :- Explain Aggregation ?Question 103 :- Explain Association ?Question 104 :- Differentiate between Composition vs Aggregation vs Association ?Question 105 :- UML Symbols for Composition, Aggregation and Association

Part 11 - Crack questions on Stack, Heap, Boxing, Unboxing, Value &  reference typesQuestion 106 :- Explain stack and Heap ?Question 107 :- Where are stack and heap stored ?Question 108 :- What goes on stack and what goes on heap ?Question 109:- How is the stack memory address arranged ?Question 110 :- How is stack memory deallocated LIFO or FIFO ?Question 111 :- How are primitive and objects stored in memory?Question 112 :- Can primitive data types be stored in heap ?Question 113 :- Explain value types and reference types ?Question 114 :- Explain byval and byref ?Question 115 :- Differentiate between copy byvalue and copy byref ?Question 116 :- What is boxing and unboxing ?Question 117 :- Is boxing unboxing good or bad ?Question 118 :- Can we avoid boxing and unboxing ?Question 119 :- What effect does boxing and unboxing have on performance ?Question 120 :- Are string allocated on stack or heap ?Question 121 :- How many stack and heaps are created for an application ?Question 122 :- How are stack and heap memory deallocated ?Question 123 :- Who clears the heap memory ?Question 124 :- Where is structure allocated Stack or Heap ?Question 125 :- Are structures copy byval or copy byref ?Question 126 :- Can structures get created on Heap ?

Part 12 - What is Garbage collector, Managed vs UnManaged code, Dispose Pattern, Memory Leaks, weak VS strong references ?

Question 127: - Explain Garbage collector (GC)?

Question 128:- How does Garbage collector know when to clean the objects ?

Question 129 :- Is there a way we can see this Heap memory ?

Question 130 :- Does Garbage collector clean primitive types ?

Question 131: - Managed vs UnManaged code/objects/resources?

Question 132:- Can garbage collector clean unmanaged code ?

Question 133:- Explain Generations  ?

Question 134:- What is

Question 135:- Why do we need Generations ?

Question 136:- Which is the best place to clean unmanaged objects ?

Question 137:- How does GC behave when we have a destructor ?

Question 138:- What do you think about empty destructor ?

Question 139:- Explain the Dispose Pattern?

Question 140 :- Finalize vs Destructor ?

Question 141:- What is the use of using keyword ?

Question 142:- Can you force Garbage collector ?

Question 143:- Is it a good practice to force GC ?

Question 144:- How can we detect a memory issues ?

Question 145:- How can we know the exact source of memory issues ?

Question 146 :- What is a memory leak ?

Question 147 :- Can .NET Application have memory leak as we have GC?

Question 148:- How to detect memory leaks in .NET applications ?

Question 149:- Explain weak and strong references ?

Question 150 :- When will you use weak references ?

Lesson 13 :- Questions around Design Pattern Basics, Types, Singleton Pattern, Prototype, Template and Adapter.

Question 151:- What are design patterns?

Question 152 :- Which are the different types of design patterns?

Question 153 :- Explain structural , Behavioral and Creational design pattern ?

Question 154:- Explain Singleton Pattern and the use of the same?

Question 155:- How did you implement singleton pattern?

Question 156:- Can we use Static class rather than using a private constructor?

Question 157:- Static vs Singleton pattern?

Question 158:- How did you implement thread safety in Singleton?

Question 159:- What is double null check in Singleton?

Question 160:- Can Singleton pattern code be made easy with Lazy keyword?

Question 161:- Can we rid of this double null check code?

Lesson 14 :- Repository Pattern and Unit of Work Design Pattern Interview Questions.

Question 162:- What is the use of repository pattern? 

Question 163:- Is Dal (Data access Layer) and Repository same? 

Question 164:- What is Generic repository pattern ?

Question 165:- Is abstraction the only benefit of Repository?

Question 166:- How to implement transaction in repository?

Question 167:- What is Unit of work design pattern?

Question 168:- Do we need repository pattern as EF does almost the same work?

Question 169:- Did you do unit testing with Repository ?

Question 170:- How does repository pattern make unit testing easy?

Question 171:- How can we do mock testing with Repository?