C# Basic

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dbt 
airflow

一、基础50

1. What is CIL?

CIL (Common Intermediate Language) is the intermediate code generated after compiling .NET programming languages such as C# and VB.NET.

2. What is CLR?

CLR is the core component of the .NET framework, responsible for managing code execution.
provides features like memory management, garbage collection (GC), security, exception handling, and multithreading. Its main task is to convert CIL into machine code and provide a runtime environment.

3. What is the difference betweent value type and reference types?

value type: stored in stack, struct, enum, int float bool,char
refrecence type: stored in heap, object, class, array,string, interface, delegate

4. what is boxing and unboxing?

value => refrence: boxing
reference => value: unboxing

5. How are exceptions handled in C#?

6. What is the difference between a class and a struct?

class: reference type, stored in heap managed by GC,

struct: value type, stored in stack,automatically deallocated

7. What does the “new” keyword do?

8. What is the purpose of the"static" keyword?

1. Static Members：The static keyword is used to declare methods, fields, properties, or constructors that belong to the class itself rather than an instance of the class.

2. A class can be declared static if it only contains static members.

3. A static constructor is used to initialize static members when the class is first accessed.

4. Even in a regular class, we can define static methods that do not depend on instance data.

5. Static fields are shared across all instances, so they must be used carefully in multi-threaded environments.

9. What is a static class?

-Cannot be instantiated – You cannot create an object of a static class.

• Only contains static members – All methods, properties, and fields must be static.
• Cannot inherit from other classes
• Improves performance
• Has an implicit private constructor

10. casting, implicit casing, explicit casting

• low data type to higher data type, implicit casting ,automaticly 1 => 1.00
• higher to lower, explicit casting

double d1 = 100.23;
int y = (int)d1 ; 

11. array VS arraylist VS Generic

• array: fixed length,strongly type
• arrayList: flexible,
• Generic List<int> intList

12. multiThread

Whitireia Community Polytechnic

Question 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 IOC
Question 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 :- Is SOLID, IOC and DI design pattern or Principle?
Question 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 types
Question 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 GC0,GC1, and  GC2 ?
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 15:- Most asked Factory Pattern, DI and IOC Interview Questions.Question 172 :- What is Factory pattern and how does it benefit?
Question 173 :- How does centralizing object creation helps in loose coupling ?
Question 174 :- What is IOC and DI ?
Question 175 :- DI vs IOC ?
Question 176 :- What is a service locator ?
Question 177:- Service Locator vs DI ?
Question 178 :- Which is good to use Service Locator or DI ?
Question 179 :- Can not we use a simple class rather than interface for DI ?
Question 180 :- Is DI a Factory Pattern?
Question 181 :- So If you just centralize object creation is it Factory pattern?
Question 182 :- Static DI and Dynamic DI ?
Question 183 :- In which scenarios to use Static DI vs Dynamic DI ?Lesson 16 :- The Real Factory and Abstract Factory Patterns.Question 184 :- The real Factory pattern ?
Question 185 :- Factory Method vs Factory pattern ?
Question 186 :- How are new behaviors created in FP ?
Question 187 :- What is Abstract Factory Pattern ?
Question 188 :- Does Abstract Factory Pattern use FP inside ?
Question 189 :- Explain Simple Factory Pattern ?
Question 190 :- Simple Factory vs Factory (Factory Method) vs Abstract Factory ?
Question 191 :- How to remove IF conditions from Simple Factory?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?Lesson 15:- Most asked Factory Pattern, DI and IOC Interview Questions.Question 172 :- What is Factory pattern and how does it benefit?
Question 173 :- How does centralizing object creation helps in loose coupling ?
Question 174 :- What is IOC and DI ?
Question 175 :- DI vs IOC ?
Question 176 :- What is a service locator ?
Question 177:- Service Locator vs DI ?
Question 178 :- Which is good to use Service Locator or DI ?
Question 179 :- Can not we use a simple class rather than interface for DI ?
Question 180 :- Is DI a Factory Pattern?
Question 181 :- So If you just centralize object creation is it Factory pattern?
Question 182 :- Static DI and Dynamic DI ?
Question 183 :- In which scenarios to use Static DI vs Dynamic DI ?Lesson 16 :- The Real Factory and Abstract Factory Patterns.Question 184 :- The real Factory pattern ?
Question 185 :- Factory Method vs Factory pattern ?
Question 186 :- How are new behaviors created in FP ?
Question 187 :- What is Abstract Factory Pattern ?
Question 188 :- Does Abstract Factory Pattern use FP inside ?
Question 189 :- Explain Simple Factory Pattern ?
Question 190 :- Simple Factory vs Factory (Factory Method) vs Abstract Factory ?
Question 191 :- How to remove IF conditions from Simple Factory?dSection 18: What is the purpose of the ternary conditional operator?
Section 19: What is the purpose of the null coalescing and null conditional operators?
Section 20: What is encapsulation?
Section 21: What is LINQ?
Section 22:What are extension methods?
Section 23:What is lEnumerable?
Section 25: What is the difference betweendeep copy and shallow copy?
Section 26: What is the Garbage Collector?
Section 27: What are nullable types?
Section 28: What is a property?
Section 29: What are generics?
Section 30:What is the difference betweenthe "const" and the "readonly" modifiers?
Section 31: What is the difference betweenthe "'ref" and the "out" keywords?
Section 32: What is the difference betweenan interface and an abstract class?
Section 33: What is polymorphism?
Section 34: What's the difference betweena virtual method and an abstract method?
Section 35: What is the methodoverloading?
Section 36: What is the difference betweenmethod overriding and method hiding?
Section 37: Does C# support multipleinheritance?
Section 38: What is the DRY principle?
Section 39: What is the "magic number"antipattern?
Section 40: Why is using the "goto"keyword considered a bad practice?
Section 41: What is the "spaghetti code"?
Section 42: What is the Singleton designpattern?
Section 43: What is the Builder designpattern?
Section 44: What is the Adapter designpattern?
Section 45: What is the Bridge designpattern?
Section 46: What is the Factory Methoddesign pattern?
Section 47: What is the "SOLD" in the SOLlDprinciples?