OOPS -1

Class- Representation of similar things in real world.

OOPS - Determine the entities from the problem definition. Identifying real life things/entities.

• Inheritance
• Encapsulation
• Polymorphism

Abstraction - Mechanism of focusing on the similarities & ignoring the differences to define class.

Class diagram-

name
------
Data member
-------------
Member Function


Objects- Instance of a class - Identity, Behavior, State.

• Difference of Abstraction (analysis level- Identifying classes) Vs Encapsulation (design level-define the class structure- data members & member functions in the same capsule)

• Inheritance- Deriving /creating a new class from the base/ existing class.

Employee -- Parent class
^
|
Manager -- Child class

• Polymorphism - static and dynamic

Static Polymorphism- Function or method Overloading - same name of methods but different number of parameters.
Dynamic or run time polymorphism - Function over-riding, using base class reference.


Data members should not be accessible outside the class. So, usually are private but then cannot use in the derived class. So, make it protected . So that they can be used in the derived clases.

To access them from outside, use property- Getters & Setters-

Trivia Info-

• To override any method, the method in the base class should be virtual.
• When assigning value to a data member via argument of a method, the data member should be prefixed with "this."
• the base constructor is referred to as 'base' in the constructors in the derived class. Same as super in java.
  
• e1==e2 ---> Checks the Reference Vs e1.Equals (e2) - Checks the values.
• 
  

Difference of foreach & for loop-

foreach (Employee e in emplist)
e.cal_sal();

foreach - the type of the list has to be mentioned.

Abstract class- not to allow instantiating, only derived class can instantiate.

Interfaces - for multiple inheritance - programming by contract - define the interface.

Sealed class - classes cannot be inherited, same as final in java, opposite of abstract class.

Association (Linking) of different classes - Aggregation & Composition.
difference of aggregation and composition>

• Aggregation - Grouping of classes- like Library and Book--> part of the whole
• Composition - Strong Aggregation-Interdependent- Car & partContents of the whole.

Inner class - a class within a class.

Exception - Run time error - use the try - catch block to avoid system crashes.

try {}
catch (Exception ex){
Console.WriteLine(ex.Message);
}

class myException :Exception {
.........
}