C#

Question 1

✅Differences Array vs ArrayList (4)

Answer 1

Array - fixed size - strong typed - force to iterate by index - faster ArrayList - re-sizable - generic typed - linq - slower

Question 2

✅ Array.Clone VS Array.CopyTo

Answer 2

Clone: returns a new array CopyTo: Copies the elements into another existing array

Question 3

✅ Abstract class vs Interface (6)

Answer 3

Abstract Class - Interface 1 - Method Signature 2 - Constructor 3 - Multiple Inheritance 4- static members 5 - access modifiers 6 - only contains methods.

Question 4

✅ Dispose vs Finalize

Answer 4

You call dispose to release a db connection, etc.

Finalize is called by the GC.
A destructor is an override version of the Finalize method, that executes the destructor’s code and then calls the base class’ Finalize method.

Question 5

✅ Struct vs Class

Answer 5

1 - Structs are value types / stored on the stack. 2- Structs don’t support inheritance 3- Structs are sealed type 4- Structs cannot have explicit parameterless constructors 5- Structs cannot have destructors

Question 6

✅ “is” vs “as” (2)

Answer 6

“is “ 1 - to check runtime type of an object. 2 - returns a boolean “as” 1 - to cast objects 2- returns an object

Question 7

✅ throw vs throw ex (1)

Answer 7

throw ex resets the stack trace, so your errors would appear to originate from HandleException throw the original offender would be preserved

Question 8

✅reflection

Answer 8

1 - dynamically create an instance of a type, 2 - bind the type to an existing object, 3- or get the type from an existing object and invoke its methods or access its fields and properties.

Question 9

✅ Unmanaged Code

Answer 9

N/A

Question 10

✅ boxing vs unboxing

Answer 10

N/A

Question 11

✅const vs readonly (1)

Answer 11

const is a compile-time constant readonly is assigned only once at run-time

Question 12

✅ ref (1) vs (2) out

Answer 12

ref 1- should be initialized before being used. out 1- isn’t required to be initialized before. 2- it is used when returning multiple parameters

Question 13

✅ string vs stringbuilder

Answer 13

N/A

Question 14

✅ SortedList (2) vs (2) SortedDictionary

Answer 14

SortedList 1 - Less memory 2- faster: if the list is populated all at once from sorted data, SortedDictionary 1- more memory 2 - faster insertion and removal operations for unsorted data, O(log n) as opposed to O(n) for SortedList

Question 15

✅ Hashtable (3) vs (2) Dictionary

Answer 15

Hashtable 1 - Non-generic 2 - not type-safe 3- Uses a hash function to choose an index to store the value Dictionary 1 - Generic 2 - Type-safe

Question 16

✅ Stack (2) vs (2) Queue

Answer 16

Stack 1- LIFO 2- Push / pop Queue 1- FIFO 2- Enqueue / Dequeue

Question 17

✅ Method overriding (2) vs (2) Method hiding

Answer 17

hiding 1 - uses the new keyword 2 - when a base class points to its child class,the base class will call the base class method override 1- uses the virtual keyword and @override over the method. 2- when a base class points to its child class the base class will call the overridden method

Question 18

✅ Int64 vs UInt64

Answer 18

U stands for unsigned integer, it stores only positive values

Question 19

✅ byte vs sbyte

Answer 19

s stands for signed integer, it stores positive and negative values

Question 20

✅ What is Lazy?

Answer 20

Lazy initialization of an object means that its creation is deferred until it is first used

Question 21

✅ Singleton VS Static Class

Answer 21

Singleton
Can implement interfaces
Can be passed as arguments
Can be assigned to variables
Can have state
Can be serialized

Static Class
No interfaces
Cannot be passed as arguments
Cannot be assigned
Can only access global state
No support for serialization