C# Fundamentals

Introduction

In the way of development of programs using FORTAN and COBAL like erlier languages the complexity was increasing for larger programs. So, the developers found out structured programing language like C. Later on these structured programing  languages also became complex in developing large projects , so developers come up with the Object Oriented programing (OOPs) language.

Structure programing works only for what is happening inside the code but does not explains which data is affecting (not works around data).

Object Oriented Programing works on both; around the code (what is happening) and around the data (which data is affecting).

To achieve the Object Oriented Programing concept we have to fallow three principles of OOPS conecpt and those are 

1.  Encapsulation
2.  PolyMorphism and
3.  Inheritance.

Let us learn about each concept

Encapsulation:

It means binding the Code and Data together; encapsulation provides security to data.

C# basic unit of encapsulation is Class, C# uses a class specification to consrtuct objects. Objects are instances of the class. Code and data are memebers of the class, the data defined in the class is field.

Polymorphism:

According to greek meaning it is "manyforms". We can describe polymorphism based on programing language like this. "Method name is same but its signature is different", it means same method name we can use more than one time within a class but its signature should be different. Signature is nothing but type of parameters or number of  parameters  passing to that method.

  
method name(signature)
{
  
 
}

For example, You drive an vehicle, which has properties like wheel size, engine size, gas tank size, and other properties. The automobile you drive is a concrete implementation of the automobile interface. It has additional features, like sliding doors, logo type, cd changer slot count, moon roof lever location, or other various properties that are specific to the make/model of the vehicle.

In OO programming, Vehicle would be the base class, and each vehicle manufacturer would have its own implementation. For instance, Maruti has K-series engine technology, which is its own implementation. Volvo uses diesel engines, which is the TDI technology. More importantly, you may add a feature in the vehicle and  implement make/model implementation, such as Car, Truck, or Suv etc.

• Polymorphism helps in decreasing the complexity of program.

Inheritence:

It means "Reusability". Inheritence is the process by which one object can import the properties of another object.

We can achive the reusability using hierarchies, if we will not use hierarchies then each object would have to explicitly  defines all of its characteristics (spcific and general characteristics). By using inheritance process  an object need only to define those qualities that make it special within its class. It can inherit its general characteristics form parent or base class object.

The concept of inheritance is used to make things from general to more specific e.g. take Animal is the general class in that we can classify animals as Mammal and Reptile () these are two derived classes of super classs Animal and dog  is a child class for both  Mammal and Animal classes .

C# is a complete Object Oriented Programming language from Microsoft that is inherently supported in .NET. Lets learn about C# now.

C# sample  program

Create a sample.cs file in Notepad and write following code.

  
using System; 
  
class sample 
  
{ 
  
static void Main()
  
{
  
Console.WriteLine("Hello World !");
  
Console.Read();
  
}
}
  

Now open the Visual Studio Command Prompt and write following line of code.

C:\> Csc sample.cs

You should be get a .exe file named sample.exe. Run this exe file by double clicking and you will see a console window opens and write the text "Hello World!" Press Enter key and that window closes.

Now let me define each line of statement one by one.

static void Main(): 

static:  a method that is declared with static keyword that method is called before an object of its class has been created.

void: it means the Main() method doesn't return a value.

In the above program if you type "main and writeline" insted of "Main and WriteLine" then compile time errors will occur. Because C# is case sensitive language and you will be forced to use the method or class name the way it has been defined in C#.

To print the result in console application Console.WriteLine(" Hello World !") is used and in web application Response.WriteLine("Hello World !") is used. In C#, all variables must be declared before they are used.

C# keywords

Keywords determines the features built in the language. C# has two types of keywords reserved and contextual keywords. The reserved keywords cannot be used as names for variables, classes and methods.

The Contextual keywords are those that have a special meanings. In special cases they act as keywords.

C# Reserved keywords

abstract	as	base	bool	break
byte	case	catch	char	checked
class	const	continue	decimal	deafult
delegate	do	double	else	enum
event	explicit	extern	false	finally
fixed	float	for	foreach	goto
if	implicit	in	int	interface
internal	is	lock	long	namespace
new	null	object	operator	out
override	params	private	protected	public
readonly	ref	return	sbyte	sealed
short	sizeof	stackalloc	static	string
struct	switch	this	throw	true
try	typeof	unit	ulong	unchecked
unsafe	ushort	using	virtual	volatile
void	while

C# Context keywords

add	dynamic	from	get	global
group	into	join	let	orderby
partial	remove	select	set	value
var	where	yeild

Identifiers

An identifier is a name assigned to a variable name, method name  or any userdefined names. Identifiers may start with Underscore (_) but should not start with a digit.  Reserved keywords of C# can be used as an identifier if it preceded by "@" otherwise not.

ex: "@for" is identifier

      "for"  is not a identifier

Reference: I have given above information from the C# 4.0 Complete reference book that I am going through.

Hope this article was useful. Do let me know your comment or feedback.