What is event bubbling ?

Server controls like Datagrid, DataList, Repeater can have other child controls inside
them. Example DataGrid can have combo box inside datagrid. These child control do not
raise there events by themselves, rather they pass the event to the container parent (which
can be a datagrid, datalist, repeater), which passed to the page as “ItemCommand” event.
As the child control send there events to parent this is termed as event bubbling.

Why is it preferred to not use finalize for clean up?

Problem with finalize is that garbage collection has to make two rounds in order to remove
objects which have finalize methods.
Below figure will make things clear regarding the two rounds of garbage collection rounds
performed for the objects having finalized methods.
In this scenario there are three objects Object1, Object2 and Object3. Object2 has the
finalize method overridden and remaining objects do not have the finalize method
overridden.
Now when garbage collector runs for the first time it searches for objects whose memory
has to free. He can see three objects but only cleans the memory for Object1 and Object3.
Object2 it pushes to the finalization queue.
Now garbage collector runs for the second time. He see’s there are no objects to be
released and then checks for the finalization queue and at this moment it clears object2
from the memory.
So if you notice that object2 was released from memory in the second round and not first.
That’s why the best practice is not to write clean up Non.NET resources in Finalize
method rather use the DISPOSE.

What is the difference between Class and structure’s ?

Following are the key differences between them :-
√ Structure are value types and classes are reference types. So structures use
stack and classes use heap.
√ Structures members can not be declared as protected, but class members can
be. You can not do inheritance in structures.
√ Structures do not require constructors while classes require.
√ Objects created from classes are terminated using Garbage collector. Structures
are not destroyed using GC.

What are similarities between Class and structure ?

Following are the similarities between classes and structures :-
√ Both can have constructors, methods, properties, fields, constants,
enumerations, events, and event handlers.
√ Structures and classes can implement interface.
√ Both of them can have constructors with and without parameter.
√ Both can have delegates and events.

What are the different accessibility levels defined in .NET ?

Following are the five levels of access modifiers :-
√ Private : Only members of class have access.
√ Protected :-All members in current class and in derived classes can access the
variables.
√ Friend (internal in C#) :- Only members in current project have access to the
elements.
√ Protected friend (protected internal in C#) :- All members in current project
and all members in derived class can access the variables.
√ Public :- All members have access in all classes and projects.

Difference between Shadowing and Overriding

Following are the differences between shadowing and overriding :-
√ Overriding redefines only the implementation while shadowing redefines the
whole element.
√ In overriding derived classes can refer the parent class element by using “ME”
keyword, but in shadowing you can access it by “MYBASE”.

What is shadowing ?

When two elements in a program have same name, one of them can hide and shadow the
other one. So in such cases the element which shadowed the main element is referenced.
Below is a sample code, there are two classes “ClsParent” and “ClsShadowedParent”. In
“ClsParent” there is a variable “x” which is a integer. “ClsShadowedParent” overrides
“ClsParent” and shadows the “x” variable to a string.
Note:- In Sample CD “WindowsShadowing” is folder which has the sample code. If you
run the program you can have two output’s one which shows a integer and other which shows
a string.
Public Class ClsParent
         Public x As Integer
End Class
Public Class ClsShadowedParent
       Inherits ClsParent 
       Public Shadows x As String
End Class

Different properties provided by Objectoriented systems

Following are characteristic’s of Object Oriented System’s :-

Abstraction
It allows complex real world to be represented in simplified manner. Example color is
abstracted to RGB. By just making the combination of these three colors we can achieve
any color in world.It’s a model of real world or concept.

Encapsulation
It is a process of hiding all the internal details of an object from the outside world.

Communication using messages
When application wants to achieve certain task it can only be done using combination of
objects. A single object can not do all the task. Example if we want to make order processing
form.We will use Customer object, Order object, Product object and Payment object to
achieve this functionality. In short these objects should communicate with each other.
This is achieved when objects send messages to each other.

Object lifetime
All objects have life time.Objects are created ,and initialized, necessary functionalities
are done and later the object is destroyed. Every object have there own state and identity
which differ from instance to instance.

Class hierarchies (Inheritance and aggregation)
This is the simplest relationship between objects. Example every customer has sales. So
Customer object and sales object have an association relation between them.

In object oriented world objects have relation and hierarchies in between them. There are
basically three kind of relationship in Object Oriented world :-
1.Association
This is the simplest relationship between objects. Example every customer has sales. So
Customer object and sales object have an association relation between them

2.Aggregation
This is also called as composition model. Example in order to make a “Accounts” class it
has use other objects example “Voucher”, “Journal” and “Cash” objects. So accounts
class is aggregation of these three objects.

3.Inheritance
Hierarchy is used to define more specialized classes based on a preexisting generalized
class. Example we have VEHICLE class and we can inherit this class make more
specialized class like CAR, which will add new attributes and use some existing qualities
of the parent class. Its shows more of a parent-child relationship. This kind of hierarchy
is called inheritance.

Polymorphism
When inheritance is used to extend a generalized class to a more specialized class, it
includes behavior of the top class(Generalized class). The inheriting class often implement
a behavior that can be somewhat different than the generalized class, but the name of the
behavior can be same. It is important that a given instance of an object use the correct
behavior, and the property of polymorphism allows this to happen automatically.

What is the relation between Classes and Objects ?

They look very much same but are not same. Class is a definition, while object is a instance of the class created. Class is a blue print while objects are actual objects existing in real world. Example we have class CAR which has attributes and methods like Speed, Brakes, Type of Car etc. Class CAR is just a prototype, now we can create real time objects which can be used to provide functionality. Example we can create a Maruti car object with 100 km speed and urgent brakes.

What is OOPS, Class and Objects?

 What is Object Oriented Programming ?
It is a problem solving technique to develop software systems. It is a technique to think real world in terms of objects. Object maps the software model to real world concept. These objects have responsibilities and provide services to application or other objects.


What’s a Class ?
A class describes all the attributes of objects, as well as the methods that implement the behavior of member objects. It’s a comprehensive data type which represents a blue print of objects. It’s a template of object.


What’s an Object ?
It is a basic unit of a system. An object is an entity that has attributes, behavior, and identity. Objects are members of a class. Attributes and behavior of an object are defined by the class definition.