Q. What is Object
Oriented Programming?
A. Object-oriented programming (OOP) is a programming paradigm using “objects”
(data structures consisting of data fields and methods together with their
interactions) to design applications and computer programs.
Q. What is an Object?
A. An object is an instance of a class.
Q. What is a Class?
A class is the blueprint from which the individual objects are created. Class
is composed of three things: a name, attributes, and operations.
Q. What is Encapsulation ?
Encapsulation implies that the non-essential details of an object are hidden
from the user and an access its provided to its essential details.
Example : Computer games also use this feature. The user only needs to
know how to play the game, the complex working of the game is hidden from the
user.
Encapsulation is the feature that provides security to the data and the methods
of a class.
Q. What is Abstraction ?
Abstraction is a process of hiding unwanted details from the user.
Abstraction also means ignoring the non-essential details of an object and
concentrating on its essential details.
Q. What is Inheritance ?
Inheritance enables you to extend the functionality of an existing class.
When you create a class that inherits another existing class, it will inherit
the attributes and behavior of that class, plus it can also have new attributes
and behavior that are specific to that class.
Advantage : Code-Resuability which result in saving time and energy.
Q. What is Polymorphism ?
Polymorphism – Poly stands for many and morph means form. So any thing that
exists in more than one form is known as polymorph.
In oops, polymorphism means assigning a different meaning to an entity in
different context.
Q. What are the different types of Inheritance ?
There are 5 types of inheritance,
a. Single Inheritence – One Super Class and One Sub class.
b. Multiple Inheritance – More than One Super Class and One Sub class
c. Multi Level Inheritance – A Class which is a Sub class of One class, becomes
a Super class for another class.
d. Hierarchical Inheritance – One Super Class and many Sub classes
e. Hybrid Inheritance – Multiple and Multi level combined.
Q. What are the different types of Polymorphism ?
There are two types of polymorphism
1. Run Time Polymorphism
2. Compile time Polymorphism
To achive the Compile Time polymorphism there two ways
Function Overloading
Operator Overloading
To achieve the Run time Polymorphism we need to use
Virtual functions
Q. What is a Virtual Function ?
Virtual functions are normal member functions of a class, which can be
over-ridden in the derived classes. The whole functionality can be replaced in
the over-riding function.
In C#, the virtual functions will be declared with a keyword ‘virtual’ and the
over-riding functions will be declared with ‘override’ key word.
Q. What is Serialization and De-Serialization?
Serialization is the process of converting an object into a series of bytes for
transmitting or storing purpose. Deserialization is a process, where these same
bytes are converted back into objects.
Q. What is an Abstract Class ?
Abstract class is a class which cannot be instantiated but it is inherited by
derived classes. This class contains abstract as well as non-abstract methods
and members.
Any concrete class (i.e not abstract) inheriting an abstract class MUST
implement ALL inherited abstract method.
Q. What is an Interface ?
Interface is a contract for what a class MUST do, but it does not specify the
way it should be done.
An interface contains only the signatures of methods (only the declaration). A
class implementing the interface must implement all the members of the
interface (i.e provide the definations for those methods).
Interface separates the implementation and defines the structure, and this
concept is very useful in cases where you need the implementation to be
flexible.
Interfaces can inherit other (many) Interfaces.
A Class can implement many Interfaces.
Q. What is the difference between Abstract class and Interface ?
An abstract class can have abstract members as well non abstract members. But
in an interface all the members are implicitly abstract and all the members of
the interface must be overriden in its derived class.
A class can inherit one or more interfaces, but only one abstract class.
An abstract class can have 0 abstract method.
Abstract class can have fields (such as int, string etc) , whereas Interface
cannot.
Q. What are the different accessibility levels that can be defined in .NET?
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.
Q. What is the difference between Class and Structure?
Structs are value types and classes are reference types. The general different
is that a reference type lives on the heap, and a value type lives inline, that
is, wherever it is your variable or field is defined.
A struct’s members are public by default while a class’ members are private by
default
Classes are reference types and structs are value types.
Q. What does virtual keyword mean?
A. It signifies that the method/property can be overridden.
Q. What are static variables?
A static member cannot be referenced through an instance. Instead it is
referenced through the class name.
An instance of a class will contain a separate copy for each instance, whereas
for static, there will be only one copy for each static field.
If static keyword is applied to a class then all members of the class must be
static.
Q. What is Finalize method in .NET?
Allows an object to try and free resources and perform other clean up
operations before it is reclaimed by garbage collection.
Q. What is Dispose method in .NET?
Dispose method belongs to ‘IDisposable’ interface. If any object wants to
release its unmanaged code, it is a good practice to implement the
‘IDisposable’ interface and then override the Dispose() method.
Q. What is the use of “Overrides” and “Overridable” keywords?
Overridable is used in parent class to indicate that a method can be
overridden. Overrides is used in the child class to indicate that you are
overriding a method
Q. Where are all .NET Collection classes located?
System.Collection namespace
Q. What is an ArrayList?
An ArrayList is a data structure. It stores data in an array that can be
dynamically resized. Array list can hold item of different types. You can
access any item in array using the INDEX value of the array position.
Q. What is a HashTable?
Hashtable optimizes lookups. This type is used in the C# language. It computes
a hash of each key you add. It then uses this hash code to look up the element
very quickly. It is an older .NET Framework type. It is slower than the generic
Dictionary type.
Code:
Hashtable
hashtable = new Hashtable();
hashtable[1] = "One";
hashtable[2] = "Two";
hashtable[13] = "Thirteen";
foreach (DictionaryEntry entry in hashtable)
{
Console.WriteLine("{0}, {1}", entry.Key, entry.Value);
}
Q. What are Collections in .NET
List
First, the List type provides you with an efficient and dynamically-allocated
array. It does not provide fast lookup in the general case, which you will want
to use Dictionary for. It is excellent when used in loops.
Code:
// Use the
List type.
List<string> list = new List<string>();
list.Add("cat");
list.Add("dog");
foreach (string element in list)
{
Console.WriteLine(element);
}
Dictionary
The Dictionary type in the base class library is one of the most important ones
you need to use for your C# programs. It is an implementation of a hashtable,
which is an extremely efficient way to store keys for lookup. The Dictionary in
.NET is well-designed.
Code:
// Use the
dictionary.
Dictionary<string, int> dict = new Dictionary<string, int>();
dict.Add("cat", 1);
dict.Add("dog", 4);
Console.WriteLine(dict["cat"]);
Console.WriteLine(dict["dog"]);
ArrayList
As shown in this program, the ArrayList is a collection found in
System.Collections and it can store objects of any derived type. You don’t need
to worry about the type of the elements, at least until you need to know their
types to use them.
Code:
ArrayList
list = new ArrayList();
list.Add("cat");
list.Add(2);
list.Add(false);
foreach (var element in list)
{
Console.WriteLine(element);
}
Hashtable
Hashtable optimizes lookups. This type is used in the C# language. It computes
a hash of each key you add. It then uses this hash code to look up the element
very quickly. It is an older .NET Framework type. It is slower than the generic
Dictionary type. First, you can create a new Hashtable with the simplest
constructor. When it is created, the Hashtable has no values. We directly
assign values with the indexer, which uses the square brackets [ ]. The example
adds three integer keys with one string value each.
Code:
Hashtable
hashtable = new Hashtable();
hashtable[1] = "One";
hashtable[2] = "Two";
hashtable[13] = "Thirteen";
foreach (DictionaryEntry entry in hashtable)
{
Console.WriteLine("{0}, {1}", entry.Key, entry.Value);
}
Stack
Stack is a LIFO collection. It provides a powerful and simple last-in-first-out
data structure. This can help you develop parsers quickly and also replace
complex recursive algorithms. Stack is a generic type.
LIFO:
The last element added (with Push) to Stack is the first one removed (with
Pop).
Code:
Stack<int>
stack = new Stack<int>();
stack.Push(100);
stack.Push(1000);
stack.Push(10000);
return stack;
Queues
Queue is a FIFO collection. It helps when you have elements that you need to
process in a first-in, first-out order. It processes the elements that you
received longest ago first. We look at several examples of using
Queue<T>. We think about some of the logic used for processing help
requests in a C# application.
First-In-First-Out:
The queue data structure implements this algorithm. Queue is a generic type
with one type parameter.
Code:
// New Queue
of integers
Queue<int> q = new Queue<int>();
q.Enqueue(5); // Add 5 to the end of the Queue.
q.Enqueue(10); // Then add 10. 5 is at the start.
q.Enqueue(15); // Then add 15.
q.Enqueue(20); // Then add 20.
Q. What is an ENUM?
It is used to define constants. Enums store special values. They make programs
simpler. If you place constants directly where used, your C# program becomes
complex. It becomes hard to change. Enums instead keep these magic constants in
a distinct type. They improve code clarity. They alleviate maintenance issues.
An enum type is a distinct value type that declares a set of named constants.
Q. What is a nested Classes?
Nested classes are classes within classes. In sample below “ClsNested” class
has a “Child
Nested” class nested inside it.
The class B here is enclosed inside the declaration of class A. Class B is thus
a nested class. Because it has a public accessibility modifier, it can be
accessed in places other than class A’s scope. In the main entry point, we
create an instance of A, and also an instance of A.B. The instance of A does
not contain an instance of B; the reverse is also the case.
Program that shows nested class B [C#]
class A
{
public int _v1;
Code:
public class
B
{
public int _v2;
}
}
class Program
{
static void Main()
{
A a = new A();
a._v1++;
A.B ab = new A.B();
ab._v2++;
}
}
Q. What is Operator overloading in .NET?
It provides a way to define and use operators such as +, -, and / for
user-defined classes or
structs. It allows us to define/redefine the way operators work with our
classes and structs. This allows programmers to make their custom types look
and feel like simple types such as int and string.
Code:
using System;
class Widget
{
public int _value;
public static Widget operator +(Widget a, Widget b)
{
// Add two Widgets together.
// … Add the two int values and return a new Widget.
Widget widget = new Widget();
widget._value = a._value + b._value;
return widget;
}
public static Widget operator ++(Widget w)
{
// Increment this widget.
w._value++;
return w;
}
}
class Program
{
static void Main()
{
// Increment widget twice.
Widget w = new Widget();
w++;
Console.WriteLine(w._value);
w++;
Console.WriteLine(w._value);
// Create another widget.
Widget g = new Widget();
g++;
Console.WriteLine(g._value);
// Add two widgets.
Widget t = w + g;
Console.WriteLine(t._value);
}
}
Output
Quote:1
2
1
3
Q. What is the significance of Finalize method in .NET?
For the majority of the objects that your application creates, you can rely on
the .NET Framework’s garbage collector to implicitly perform all the necessary
memory management tasks. However, when you create objects that encapsulate
unmanaged resources, you must explicitly release the unmanaged resources when
you are finished using them in your application. The most common type of
unmanaged resource is an object that wraps an operating system resource, such
as a file, window, or network connection. Although the garbage collector is
able to track the lifetime of an object that encapsulates an unmanaged
resource, it does not have specific knowledge about how to clean up the
resource. For these types of objects, the .NET Framework provides the
Object.Finalize method, which allows an object to clean up its unmanaged
resources properly when the garbage collector reclaims the memory used by the
object. By default, the Finalize method does nothing. If you want the garbage
collector to perform cleanup operations on your object before it reclaims the
object’s memory, you must override the Finalize method in your class.
Q. What is the use of DISPOSE method?
Dispose method belongs to ‘IDisposable’ interface. We had seen in the previous
section how bad it can be to override the finalize method for writing the
cleaning of unmanaged resources. So if any object wants to release its
unmanaged code best is to implement I Disposable and override the Dispose
method of I Disposable interface. Now once your class has exposed the Dispose
method it is the responsibility of the client to call the Dispose method to do
the cleanup.
Q. In what instances you will declare a constructor to be private?
When we create a private constructor, we cannot create object of the class
directly from a client.
Therefore, you will use private constructors when you do not want instances of
the class to be created by any external client. Example UTILITY functions in
project will have no instance and be used with out creating instance, as
creating instances of the class would be waste of memory.
Q. Can two catch blocks be executed?
No, once the proper catch section is executed the control goes finally to
block. So there will not be any scenarios in which multiple catch blocks will
be executed.
Q. What is the difference between System.String and System.StringBuilder
System. String is immutable;
System.StringBuilder can have mutable string where a variety of operations can
be performed.
Jquery Question Answers
Q1. What is Jquery in
the context of web applications?
jQuery is nothing but a collection of well written JavaScript code.
In other words Jquery is ready made concise and fast JavaScript Library to be
used.
Q2. What are the advantages of using jQuery over JavaScript in ASP.NET web
application
Below are the advantages of using jQery over JavaScript
1.Jquery is well written optimised javascript code so it will be faster in
execution unless we write same standard optimised javascript code.
2.Jquery is concise java script code ,means minimal amount of code is to be
written for the same functionality than the javascript.
3.Javascript related Development is fast using Jquery because most of the
functionality is already written in the library and we just need to use that.
4.Jquery has cross browser support ,so we save time for supporting all the
browsers.
Q3. How to use jQuery in ASP.NET web application?
To use jQuery in ASP.NET web application follow the below steps:
a)Go to http://jquery.com/(The official jQuery WebSite)
b)Download latest .js jQuery file from the website.
c)Put it the script(or other folder) in the root of your web application
d)Add the below tag on the page where you want to use Jquery script
type="text/javascript"
src="script/jQueryDownLoadedFileName.js" /script
Q4. What is the use of Jquery min js file in ASP.NET web application
JQuery min .js file is actully a minified version of Actual JQuery .js. The min
files have less size but same content so this improves the performance.so You
should prefer to use min files.
Q5. What is the advantages of use of document.ready functions in jQuery
Advantage of using $(document).ready(function () in jQuery is that the code
inside this function will execute only when the full page has been loaded so
that there will be no error like the DOM object on which the Jquery has to
execute is not loaded.
Q6. Can we write more than one document.ready jQuery functions in one page
Yes we can write more than one jquery $(document).ready(function () in one
page.This is helpful when you have large Jquery code and you want to split it
in multiple files.
Q7. How to select an element with Id in Jquery
To select an element with Id write as below:
var divValue = $(''#sampleDivId'').val();
Q8. How to select an element with class in Jquery
To select an element with class write as below:
$(".sampleClass").css("border","2px solid blue");
Q9. What is the difference between jQuery find and children methods
The difference between find() and children() methods are that the children only
travels a single level down the DOM tree while the find travels at all level
down the DOM tree.
Q10. How to use length function in jQuery to text existence of an element by
Id
To test if an element exists we can use length method in jQuery as below:
if $(''#mySampleDiv'').length )//Tests wheter the div with id mySampleDiv
exists or not $(mySampleDiv).find(''div'');
