021 C# Program Stucture

Program Stucture
You are going to write a simple program to get simple knowledge on C# program structure. To write a simple program we need to know about structure of  program. Here are the list of preliminary need to know before writing a simple program.

•  namespace 
•  method 
•  function 
•  comments multi line
•  comments single line delete statement 
•  class 
•  main method

Below is a is the simple program of hello world. When you run this program, the program print the string "hello world" in the screen.

using System;

namespace student

{

         class student

         {

               public double Gatefees()

              {

                  double fees=300.65;

                  return fees;

             }

            static void main(string[] arg)

                  {

                      //Here is single line comments

                      /*Here is the exaple of 

                   multiline comments */

                   Console.WriteLine("hello world");

                }

      }

}

using system : system is a class at the root level. All other class of. Net comes under system class. System class is the namespace fundamental classes. The system namespace provides ,variable data type , like value type and reference type, event Handler, methods. using keyword tells the compiler, the component under system namespace will be available in this program. Generally a complex program have multiple using statement to include well namespace and functionality in it.

namespace student : namespace student keyword tells the compiler, class is declared under which namespace available only when this namespace is used. We have declared the class student, this will be available only, when a statement using student will be written at the top of the program. Namespace is a collection of classes, it can contain one or more classes. Here student is a namespace and student is the class under this namespace.

The next line is  a class declaration, a class is a template of an object. A class contain one or more method and variables. Here are student class accountant two method. The method, Gatefees will return the fees when it is called.

The main method is entry point of a program, when a program start running the main method is called fast.


Some points you should keep in mind

•  C# is case sensitive 
•  every C# statement ends with a semicolon 
•  every C# program starts from A main method. 
•  namespace must be included to get required component. The highest level of new namespace is system.

You have seen the hello world program,  now you will see how to create this program.

1) create project-->Empty project

2) a new project is created

3) add a c# source file ,Solution Explores-->Add-->New Item-- Code File-->> Name it student.cs

4)Write program in student.cs

5)Compile from built menu

6)Press F5

handling Syntax error : When a software engineer write program it is obvious that there will be some mistake on typing.. Net Framework is intelligent enough to report the error at the compile time. Engineer resolve the problem and compile again.. Net Framework is intelligence enough,it show possible resolution hints. Most of the time the hints works successfully and resolve the issue. But sometimes mislead the engineer in a wrong way.

C# keyword : Every language have some keyword to identify its features. This features active language structure. C# some keyword also. There are two type of Keyword reserve keyword and contextual keyword. Reserved keyword are the keywords that has been reserved by the C# own use. No variable, method, class can be declared with this name. Contextual keyword have some special meaning for some context, out of context this keyword can be used. Here is the list of some reserved keyword C#

Here is the list of reserved keyword by C#
 

abstract	add	as	ascending
async	await	base	bool
break	by	byte	case
catch	char	checked	class
const	continue	decimal	default
delegate	descending	do	double
dynamic	else	enum	equals
explicit	extern	false	finally
fixed	float	for	foreach
from	get	global	goto
group	if	implicit	in
int	interface	internal	into
is	join	let	lock
long	namespace	new	null
object	on	operator	orderby
out	override	params	partial
private	protected	public	readonly
ref	remove	return	sbyte
sealed	select	set	short
sizeof	stackalloc	static	string
struct	switch	this	throw
true	try	typeof	uint
ulong	unchecked	unsafe	ushort
using	value	var	virtual
void	volatile	where	while
yield

 Here is Some of contextual keyword by C#

• add    

• alias    

• ascending

• async    

• await    

• descending

• dynamic    

• from    

• get