C# Keywords and Identifiers

C# Keywords and Identifiers: In this tutorial, we will learn about watchwords (reserved words) and identifiers in C# programming language.

A keyword is a reserved word. You can’t use it as a variable name, constant name and so forth

In C# keywords can’t be used as identifiers. Be that as it may, on the off chance that we need to use the keywords as identifiers, we may prefix the keyword with @ character.

C# Keywords

Keywords are predefined sets of reserved words that have special meaning in a program. The significance of watchwords can not be changed, neither would they be able to be straightforwardly used as identifiers in a program.

For instance,

long mobileNum;

Here, long is a watchword and mobileNum is a variable (identifier). long has a special meaning in C# for example it is used to declare variables of type long and this function can’t be changed.

Likewise, watchwords like long, int, char, and so on can not be used as identifiers. Along these lines, we can’t have something like:

long long;

C# has a total of 79 watchwords. Every one of these catchphrases are in lowercase. Here is a finished rundown of all C# watchwords.

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

Although keywords are reserved words, they can be used as identifiers if @ is added as prefix. For instance,

int @void;

The above statement will create a variable @void of type int.

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Contextual Keywords

Other than ordinary catchphrases, C# has 25 relevant watchwords. Contextual catchphrases have specific meaning in a limited program context and can be used as identifiers outside that unique circumstance. They are not reserved words in C#.

add	alias	ascending
async	await	descending
dynamic	from	get
global	group	into
join	let	orderby
partial (type)	partial (method)	remove
select	set	value
var	when (filter condition)	where (generic type constraint)
yield

On the off chance that you are interested to know the function of each watchword, I recommend you visit C# keywords (official C# docs).

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C# Identifiers

Identifiers are the name given to entities like variables, methods, classes, and so on They are tokens in a program which uniquely recognize an element. For instance,

int value;

Here, value is the name of variable. Henceforth it is an identifier. Reserved catchphrases can not be used as identifiers unless if @ is added as prefix. For instance,

int break;

This statement will generate an error in compile time.

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Rules for Naming an Identifier

• An identifier can not be a C# keyword.

• An identifier should start with a letter, an underscore or @ symbol. The excess piece of identifier can contain letters, digits and underscore symbol.

• Whitespaces are not allowed. Neither one of the its can have symbols other than letter, digits and underscore.

• Identifiers are case-touchy. In this way, getName, GetName and getname addresses 3 different identifiers.

Here are a portion of the legitimate and invalid identifiers:

Identifiers	Remarks
number	Valid
calculateMarks	Valid
hello$	Invalid (Contains $)
name1	Valid
@if	Valid (Keyword with prefix @)
if	Invalid (C# Keyword)
My name	Invalid (Contains whitespace)
_hello_hi	Valid

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Example: Find list of keywords and identifiers in a program

Just to clear the idea, let’s discover the list of watchwords and identifiers in the program we wrote in C# Hello World.

using System;
namespace HelloWorld
{
    class Hello
{         
        static void Main(string[] args)
        {
          Console.WriteLine("Hello World!");
        }
    }
}

Keywords	Identifiers
using	System
namespace	HelloWorld (namespace)
class	Hello (class)
static	Main (method)
void	args
string	Console
	WriteLine

The “Hello World!” inside WriteLine method is a string literal.

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C# Introduction