1. What is a Framework?
A framework is software which masks
the functionality of the operating system and makes the code to execute under
its control. Which provides basic features like?
· Platform Independency
· Security
· Memory Management.
2. What are the features
of C#2.0?
· Partial classes which allows class implementation a cross more than one
source file. This permits splitting up very large classes.
· Generics or Parameterized types.
· Static classes that can’t be instantiated
· Null able value types which provides improved interaction with SQL
Databases.
3. Features of C# 3.0
· LINQ(Language Integrated Query)
· Object initializes and Collection Initializes
· Anonymous Types
· Implicitly typed variables(Using Var Keyword)
· Lambda expressions
· Automatic Properties
· Extension Methods
· Partial Methods
4. Implicitly Typed
Variables
This is a new feature which allows
declaring a variable using the keyword “VAR” .The data type of variable is
decided according to the value assigned to the variable.
Example:
Var x=100 integer
Var s=”hello” String
5. Boxing and UN Boxing
When a value type is stored as
reference type in the heap memory we called it as a boxing
E.g. Object OBJ=100;
If the value type in the heap is
converted and send back to stack we called as UN boxing
E.g. int x=convert.toInt32 (OBJ);
6. Object Oriented
Programming
A language to be called as object
oriented needs to satisfy a set of basic principles like
· Encapsulation
· Abstraction
· Inheritance
· Polymorphism
Encapsulation:
According to this the code in an
object oriented language as to be warped in a container called as class which
provides security to the class.
Abstraction:
It is an approach which talks about
hiding the complexity by providing a set of interfaces to consume the
functionality.
Inheritance:
According to this member of the class
can be accessed by another class if they have parent child relationship.
Polymorphism:
Entities behaving in different ways
depending upon the input they received are known as polymorphism
7. What is a
constructor?
· A constructor is a special method available under every class responsible
for initializing the variables of a class
· The name of the constructor is same as class name
· A constructor method never returns a value
· Without a constructor a class never executes.
8. Class Members
Whatever we define under a class were
known as class members like variables, methods, constructors
9. Instance variables
vs. static variables
A variable declared using static
modifier or declared under static block were known as static variable rest of
all “Instance variable”
Instance variable initialized
whenever the object of the class get created. So the minimum or the maximum no
of times it gets initialized will be Zero or N.
Where as a static variable gets
initialized once the execution of the class starts. So the minimum and maximum
no of times it gets initialized is only one.
10. Instance
constructor and static constructor
· A constructor declared using static modifier is a static constructor,
rest all instance constructors.
· Static constructor responsible for initialize the static variable and
instance constructor is initializing instance variable.
· A static constructor gets called one and only once in the execution of a
class i.e. when the class execution starts.
· Whereas instance constructor gets called zero (or) ‘N’ times i.e. each
time the object of the class gets created.
· As we can pass parameters to an instance constructor it cannot be done in
the case of static constructor because a static constructor never takes
parameters or cannot be parameterized.
11. Extension Methods
It was a new concept added in c#3.0
specification that allows you to extends the functionalities of class i.e.
adding methods under the class even if you don’t have source code or you don’t
have the permission to edit a class
The advantage of this approach is
that after adding the method to a class you can call the methods using object
of the class.
· Extension methods can be define only under static class
· Because they were defined under the static classes they will be defined
as static methods but while consuming should be access as instance methods only
· The first parameter of an extension method is the linker parameters which
specifies to which class the method belongs prefixed with ‘this’ keyword. While
calling the parameter will not be consider.
· If you want any parameters to extension method while defining they should
start from 2nd parameter.
Syntax:
Public static void test (this
original obj, int x){}
12. Overloading
This allows defining of multiple
methods or constructors with the same name by changing their parameters’ or
signatures.
Overloading is an approach which
allows providing multiple behaviors to a method
Example: Write and write line methods
of the console class which were provided with different overloads to print
different type of values.
Change in signature can be any of the
following
· Change the number of parameters being passed to a method
· Type of parameters being passed to a method
· Change the order of the parameter passed to a method
Example:
Class loadDemo
{
Public
void show ()
{
Console.writeline(1);
}
Public void show (int a,int b)
{
Console.writeline(a+b);
}
}
13. Method Overriding
If a method of parent class is
redefined in the child class with the same signature, we called it as “Method
Overriding”.
Example:
Class parent
{
Public void test()
{
Console.writeline(1);
}
Public virtual void test(int x,int y)
{
Console.writeline(x+y);
}
}
Class child:parent
{
Public void method1()
{//some method
}
Public override void test(int x,int y)
{
//do something
}
}
14. Difference between
Overloading and Overriding.
Overloading
Overriding
1. This allows defining multiple 1. This allows defining multiple
Methods with the same name methods with the same name
by changing their signature. And same signature
2. This can be performed with 2. This can be performed with in
In the class or child class the child class only.
3. When performed under the 3.To perform this you require
Child class doesn’t require any on explicit permission from
permission from the parent. the parent.
15. How does the parent
class give the permission to the child class to override or re-define in the
method?
The parent class gives the permission
to the child class to re-define the method by declaring the method as “virtual”
now the child class can override the method, on optional basis using the
override modifier.
Example:
Public virtual void test (int x) {}//parent
class method
Public override void test (int x) {}//child
class override method
16. After overriding a
method under a child class can we invoke the virtual method of parent from the
child class.
Yes. This can be done in two ways
1.
Create the object of the
parent class under the child class to invoke the virtual method.
2.
Using the base keyword
also you can invoke the virtual method of parent from child after overloading.
17. Can we rewrite a
method under child class without permission from parent?
Yes, we can re-write a method under
child without the permission from parent also (i.e. not declared as virtual)
but we called this a “Method –Hiding”.
In case of overriding we use the
override modifier to re-write the method
Where as in case of method-hiding we
use New modifier for rewriting the
method.
18. How to restrict a
class not to be inherited by any other class.
If we want to restrict a class not to
be inherited by any other class it should be declare using sealed modifier.
19. Abstract methods
and Abstract Classes.
A method without any body is known as
an abstract method what it has only the signature of the method. The class
under which you define these abstract methods is called as abstract class.
Abstract class can contain non abstract methods also.
Example:
Abstract Class math
{
Public void test ()
{//do something
}
Public abstract void add (int a,int b);
}
20. Interfaces
In object oriented programming we can
also declare abstract members under another container called as interface apart
from abstract class. But these interfaces can contain only abstract members in
it.
As we know that multiple inheritances
is not supported through classes, but it was still supported with “interfaces”
i.e. a class can have only one immediate base class to it but can have multiple
immediate interfaces are parent.
21. Partial classes
It was an approach of defining a
class in more than one file i.e. u can split in class into multiple files.
Partial classes provide the following benefits.
· Splitting up huge
volume of code into multiple files which makes easy to manage
· Multiple programmers can work on the same class at a time.
Example:
Class parts partial class parts partial class parts
{
{ {
Method1 () Method1 () Method3 ()
Method2 () Method2 () Method4
()
Method3 () } }
Method4 ()
}
22. How to restrict a
class not to be accessible to any other class.
This can be done by declaring the
constructor of the class as private.
23. How to restrict a
class not to be inherited to any other class?
This can be done by declaring class
as sealed.
24. How to restrict a
class not to be accessible for any other class to consume it by creating its
object.
This can be done by declaring
constructor of the class as protected.
24 Members of the class
As we were aware a class is a
collection of members and these members can be of various types like
· Fields(variables)
· Methods
· Constructors
· Properties
· Delegates
· Events
· Enumerators
Properties: when you want to access to values of a class outside the class this can
be done in two ways.
1.
Public variables
2.
Properties
In case of variables if access is
provided the user has a chance of getting as well as setting the values the
property can be restricted in three ways
1.
Read write Property: Which
provides Get and Set Access
2.
Read Only Property: Which
provides only Get Access
3.
Write Only Property: Which
provides only Set Access
Enumerations:
It is a type with a set of predefined
values you can use these values while defining enumerated properties
Enumerated property in the sense a
property which you can restrict the values being assigned with the values
declared under enumeration.
25. Delegates
These were pointers to methods
whenever we call a method to execute a method it creates a “stack” and
destroys. Each time the method is called a stack is created and destroyed.
If you want to call a method for
multiple times without multiple stacks getting created and destroyed make use
of a “Delegate”.
Syntax:
<Modifiers>
delegate<type/void><name> [<parameters>]
Delegates are of two
types
1.
Single cast Delegates
2.
Multi cast Delegates
If a delegate is used
for calling a single method is called as single cast delegate
If a delegate is user
for calling more than one method is known as “Multi cast delegate”.
Note: If we want to
call more than one method with delegate the Input/output parameters of all the
methods should be same.
Example:
Class math
{
Public
void add (int x,int y)
{
Console.writeline(“add”,(x+y));
}
Public
void sub (int x,int y)
{
Console.writeline(“sub”,(x-y));
}
Public
void mul(int x,int y)
{
Console.writeline(“mul”,(x*Y));
}
Public
delegate
void multidel(int x,int y);
Static
void main ()
{
Math
obj= new math ();
Multidel
md= new Multidel(obj.add);
Md+=obj.sub;
Md+=obj.mul;
Md+=obj.mul;
Md(150,25);
Console.writeline();
}
}
26. Why
it is must for a child class to provide the implementation for all abstract
methods of its parents?
We can never create the
object of a class which contains any abstract method in it. An abstract class
is never useful to itself it can be consumed only by the child class that to
after providing the implementation for abstract methods of the parent.
27. How
were exceptions implemented in our Language?
Every exception was
implemented in the form of a class under the system namespace mostly the parent
class for all the exception is the class exception.
28. How
does an exception come into picture?
In the process of
execution whenever the CLR recognized a problem in the code will invoke the
exception manager which recognizes the type of exception and creates the object
of related exception class and through it.
The object thrown by
the exception manager will abnormally termination the program and displays
related error-message.
29. How
can we handle an exception?
We can handle an
exception using blocks of code known as “try-catch blocks”.
Finally Block: This was
another block of code which can be paired with try. The statements we write
under this block will execute at any code i.e. when an exception occurred or
not.
30.
Collections
·
These were objects similar to arrays
but can hold a set of dissimilar type values
·
Arrays are fixed length where as
collections are variable length which can increase the size when new values
being adding to the collection
·
Under .net we were provided with no
of collection classes like stack, queue, linked list, sorted list, array list
etc which were available under the System. Collection name space
31. Array
List
·
These were same as array, which can
hold dissimilar type values and also dynamic in size.
·
While creating the object of any
collection we can use its default constructors of a parameterized constructor
using which you can specify the initial capacity.
·
When the default constructor was used
the initial capacity will be zero by default which becomes Four the first value
gets added from then it keeps on doubling the capacity whenever required
32. What
is the difference between array and array list?
Array
Arraylist
1. It is similar type
values 1. It is a dissimilar
type values
2. It is fixed length
i.e. fixed size 2.It is variable length i.e.
Dynamic
in size.
3. It is under system
namespace 3.It is under collection
Namespace
Example: on stack
Class program
{ Static
void main (string [] args)
{
Stack
s= new Stack ();
s.
push(10);s. push(“hello”);s. push(12.35);
foreach(object
obj in s)
console.writeline(obj+””);
console.writeline(s.pop());
foreach(object obj in s)
console.writeline(obj+””);
console.read();
}
}
Example: Array List
Using System. Collections;
Namespace call project
{
Class
class1
{
Static
void main (string [] args)
{
Array
List list= new Array List ();
Console.
writeline(list.capacity);
List.add(10);
Console.writeline(list.capacity);
List.
Add(45.6); List.add(20);
List.add(false);
List
.add(“hello”);
Foreach(object
obj in list)
Console.write (obj+” ”);
Console.read();
}
}
}
33.
Generic collection. These were newly added in the, net
2.0 specifications which were similar to collection in size or capacity but can
hold only similar type of values like an Array.
Generic collection
classes are available under system. Collections generic namespace while
creating object of a generic collection we can specify the type of value it can
hold
Syntax: stack<type
t>
Example:
Class class2
{
Static
void main (string [] args)
{
List <int> list = new
List<int>();
List.Add(10);List.Add(20);List.Add(30);
Foreach(int i in List)
Console.write(i+””);
Console.read();
}
}
34.
Assemblies
·
An assembly is a unit of file that
contains IL code corresponding to your project when it was complied.
·
The name of the assembly will be the
same as project name from which it was created.
·
Assemblies were known as “unit of
deployment” because once the application development is done what we install on
client machine is assemblies only
·
An assembly file can have an
extension of either exe or dll.
Assemblies are of two
types
1.
Private Assembly
2.
Shared Assembly
Private Assembly:
By default every
assembly is private, if the reference of these assemblies was added to any project;
a copy of the assembly is created and given to the project, so each project
maintains a private copy of the assembly.
Shared
Assembly:
An assembly that was
copied in to GAC (Global Assembly Cache) was known as “Shared Assembly”. If an
assembly was shared multiple copies will not be created even if being consumed
by multiple projects, only a single copy under GAC serves the entire project.
GAC was a folder under
the windows Folder:
C:\windows\assemblyß-------GAC Folder
Note: All the BCL were
shared dll assemblies so we can find then under the GAC.
35. What
assemblies are copied in to GAC?
We can copy only strong
named assemblies in to GAC.
36. What
is a strong named Assembly?
An assembly which has 3
attributes like name, version and public key token value were known as “Strong
Named Assemblies”.
37. How
to generate a public key token?
To generate a public
key token value we were provided with a tool strong name utility, which is a
command like tool that should be used from Visual Studio command prompt as
follows
Sn –k<filename>
Example: sn –k key.snk
38. What
assembly contains internally?
An assembly internally
contains 3 major things in it.
·
Manifest Info
·
Type Metadata
·
IL Code
Manifest
Info: It contains information about the attributes that
are associated with an assembly like Title, Description, Company, and Version.
Type Meta
data: It contains the information about all the types
under Assembly like Namespace, Classes, and their members Structures,
Interfaces etc. Type metadata only describes about contents of an assembly so
an assembly can be called as self describing unit of execution.
IL Code: These are language instructions we have defined which can be understood
by CLR.
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