Data Types

Question 1

Namespace

Answer 1

Namespaces provide a hierarchical means of organizing C# programs and libraries.

Namespaces contain types and other namespaces—for example, the System namespace contains many types, such as the Console class referenced in the program, and many other namespaces, such as IO and Collections

Question 2

using

Answer 2

A using directive that references a given namespace enables unqualified use of the types that are members of that namespace.

Because of the using directive, the program can use Console.WriteLine as shorthand for System.Console.WriteLine

Question 3

Access Modifiers

Answer 3

1. public: Access isn’t restricted.
2. private: Access is limited to the containing type, only in same class
3. file: The declared type is only visible in the current source file.
   File scoped types are generally used for source generators.
4. internal: Access is limited to the current assembly.- only in assembly, same namespace/ project
5. protected: Access is limited to the containing class
   or types derived from the containing class- class and the classes
   that derived from it

Question 4

2 types of protected acess modifiers

Answer 4

proteced: private and internal

1. private protected: Access is limited to the containing class or
   types derived from the containing class within the current assembly
2. protected internal: Access is limited to the current
   assembly or types derived from the containing class.

W C# oraz .NET, assembly to podstawowy blok wykonywalny aplikacji, który może być plikiem wykonywalnym (.exe) lub biblioteką (.dll).

Assembly to jednostka wdrożenia, która zawiera kod, zasoby, a także informacje o metadanych niezbędne do wykonania tego kodu.

Termin current assembly odnosi się do tego konkretnego assembly, w którym aktualnie znajduje się kod, czyli kod wykonujący się w danym momencie. Jest to po prostu assembly, w którym znajduje się definicja klasy lub członka, którego dotyczy kontrola dostępu.

Question 5

2 types of values

Answer 5

based on how they occupy the memory
1. value type
2. reference type

Question 6

value type

Answer 6

stored directly
typically stored in stack

Question 7

reference type

Answer 7

stores the memory location of data, variable

stores memory reference, not value directly

Question 8

value type

Answer 8

1. primitives
2. nullable version
3. struct
4. enum

Question 9

reference type

Answer 9

1. class
2. interface
3. array
4. delegates
5. string

acdis

Question 10

Primitive data types

Answer 10

1. integral- sbyte, short, integer, long
2. floating point- float, double, decimal
3. boolean-bool
4. unicode characters

Question 11

2 types of conversion

Answer 11

implicit- no risk of losing data
explicit- with risk of losing data, double to int

Question 12

var

Answer 12

-from c# 3.0, to declare local variables
-compiler determines the data type
-cannot be null

Question 13

Encapsulation

Answer 13

Encapsulation- practice of hiding the internal state of an object and allowing access and modification through methods

-Data integrity
-Reduce complexity
-Abstraction- hide the implementation details

Question 14

Private field logic

Answer 14

public property- getters and setters accessors, control access

Question 15

auto-implemented properties

Answer 15

automaticlly creates a field ,
automaticlly creats a getter and a setter

Question 16

Finalizer/Destructor

Answer 16

• class can have only one finalizer, define with ~, cannot be overloaded or inherited
  -when object is destroyed, is out of scoped
  -cleanup statement

Question 17

Inheritance

Answer 17

define a class within another class,
A class can inherint from a single class and multiple interfaces

Question 18

virtual keyword

Answer 18

can be overridden in classes that inherits from this class
then we use override keyword

Question 19

Polymorhpish

Answer 19

using new keyword in the method is not a overrridening but giving higher priority

Question 20

sealed keyword-

Answer 20

the method or a class cannot be overridden

Question 21

abstract class

Answer 21

class- cannot create an instance of abstract class, just the blueprint

method- a method that has to be implemented!

Question 22

to compare if is an instance of a class-

Answer 22

as/ is keyword
Cube iceCube = element as Cube
if element is Cube

Question 23

Abstract classes and interfaces

Answer 23

cant create an instance of it

both support polymorphism

Question 24

Abstract classes and interfaces compare

Answer 24

Abstract classes:

can have constructor

can be partially implemented

can contain fields

only one inherit

-> AND Interfaces cant and class implement many

Question 25

Reading a file

Answer 25

System.IO.File.ReadAllText

Question 26

Writing to a file

Answer 26

File.WriteAllLines(path, file)
using(System.StreamWriter file = new StreamWriter()

Question 27

3 types of collection

Answer 27

1. Array
2. List
3. ArrayList

Question 28

Array

Answer 28

-fixed size
-generic- everything has to be same sized

Question 29

List

Answer 29

• can be resized dynamically but arrays cannot.
  –generic- everything has to be same sized
• can accept null as a valid value for reference types and it
  also allows duplicate elements.

Question 30

ArrayList

Answer 30

-is resizeable
-can have object of diffrent type
-cannot implement a multi-dimensional
array using ArrayList.

Question 31

Multi-dimensional array

Answer 31

[,] - two dimensioms array- matrix
[,,] - three dimensions array
.Rank- returns a dimension of an array

Question 32

Jagged Array-

Answer 32

an array inside an array
int[][] jaggedArr= new int[3][]

array with 3 arrays

Question 33

params keyword-

Answer 33

Dictionaries- generic collections