C#(Second Day)
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Transcript of C#(Second Day)
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C#
HCL Infosystems Ltd.
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Hierarchy
Namespace
Classes, Structure, Enumerators
Field, Methods, Indexeres, Delegates
Examples
System namesapace
Console class
Write() method
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Importing namespaces
Use the using keyword
using System;
Console.WriteLine(Hello);
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Creating Aliases
A method to define the alias or shortcut to some class or interface or
structure
Use the using keyword
using =;
e.g.
using c=System.Console;
c.WriteLine(Hello);
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Data types
Divided into two categories
Primitive or Value type
Reference Types
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Primitive or Value type
That holds values
Integrals
byte byte
short 2 byte
int 4 byte
long 8 byte
sbyte
ushort
uint
ulong
Floatings
floa
t 4 bytes 6 dec
plac
e double 8 bytes 14 dec place
decimal 16 bytes 28 dec place
Character
char 2 bytes
Booleans
bool 2 bytes
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Reference Types
string
object
Difference between in value type and reference type
Value types are stored in stack and reference in heap
Value types can never have null value assigned
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View contents of a exe file or MSIL code
Use ILDASM tool to view MSIL code
ILDASM filename.exe
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Reading Data from Keyboard
Use ReadLine() method of Console class
To convert data from String to other value types use
Parse() method of data types
We can also methods from Convert class
long Convert.ToInt64()
int Convert.ToInt32()
short Convert.ToInt16()
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Usage of @
Neutralize the meaning of escape sequence characters
Use keyword as identifier
Remove the escape sequence effect
Break stings in multi-line
string s=@ c:\amit;
Spead a string into multiple lines
string s=@ Amit
Kumar
Sharm
a;
Allow to use a keyword as indentfier
int @float;
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Conditional Statements
if
switch
ternary operator (?:)
Shortcut of if-else
Condition?true part:false part;
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Loops
while loop
do-while loop
for loop
foreach loop works with arrays and collections
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Class and Object
Aclass is a template or set of specifications to create similar set of
objects
An object is the real entity that takes some memory space for its
fields and executes its members
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Types ofmembers
Non-static or instance members always require an object to call
them
Static members or Class members Do not require any object to
call them. Accessible directly though the class name. static keyword
is required.
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Classification ofmembers
Fields to hold the value
Variable - default
Constants const keyword required and value must be
assigned while declaration
const double pi=31.4;
ReadOnly Fields Value can be assigned directly or using
constru
ctor. readonly keyword required
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Methods to do some action
Constructor
Destructor
Concrete Methods or General methods
Abstract methods
Sealed method
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Constructor
Special method which has the same name as
class
No return type
Used to initialize fields ofaclass
Can be overlo
aded
Can be private
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Destructor
Special methods which has the same name
as class name preceded by tild (~)
Calls automatically when object releases the
memory
Cannot be overloaded
By default is public, public keyword is not
allowed to use
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Abstract methods
A methods having only the signature but no body
contents
Contents are provide by overriding the methods in
child class
If declared in class, abstract keyword is required and
if declared inside an interface, no abstract keyword
required
Ifaclass contains any abstract method, it must be
declared as abstract
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Sealed method
A method that can never be overridden
sealed keyword is required
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Difference between const and readonly field
In const value must be give while declaring the
constants
const int n=5;
Readonly field can have the value while
declaration or using constructors
readonly int n;
readonly int n=5;
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Properties
Special methods that looks like fields for outside world
set and get are used to create the properties
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datatype variable;
{
set
{
Variable=value;
}
get
{
Return variable;
}
}
Objectname.propetyname=anyvalue; //set
Variable=objectname.propertyname; //get
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Types ofproperties
Read/Write properties
Having set and get
Read Only properties
Having only get
Write Only properties
Having only set
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Passing arguments to the methods
Pass by value (default)
Pass by reference (ref keyword)
When values from actual arguments get passed to formal
arguments and if we make any changes to format arguments,
they are reflected in actual arguments
Pass By output (out keyword)
To senda
variable to re
ceive the output
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Difference between ref and out
In pass by ref, variable must be initialized by in out no initialization
required
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Pillars of OOPs
Encapsulation
All members should be bundled in one body
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Abstraction orData Hiding
Provides accessibility control on the members
It is based on certain keywords
private
public
protected
internal (default)
protected internal
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Polymorphism
A method to achieve multiple activities from an item
It is achieve using the concept of overloading
Method Overloading
Operator Overloading
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Inheritance
Provides re-usability ofcode
.NET allows only single inheritance
It allows to use multiple interfaces
Use : operator to inherit aclass or interface into other
class or interface