Working with Variables, Operators, and Expressions in Microsoft Visual C#

12/15/2012

Contents

Using Identifiers

Identifiers are the names you use to identify the elements in your programs, such as namespaces, classes, methods, and variables. (You will learn about variables shortly.) In C#, you must adhere to the following syntax rules when choosing identifiers:

You can use only letters (uppercase and lowercase), digits, and underscore characters.
An identifier must start with a letter or an underscore.

For example, result, _score, footballTeam, and plan9 are all valid identifiers, whereas result%, footballTeam$, and 9plan are not.

Identifying Keywords

The C# language reserves 77 identifiers for its own use, and you cannot reuse these identifiers for your own purposes. These identifiers are called keywords, and each has a particular meaning. Examples of keywords are class, namespace, and using. You’ll learn the meaning of most of the C# keywords as you proceed through this book. The following table lists the keywords:

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

C# also uses the following identifiers. These identifiers are not reserved by C#, which means that you can use these names as identifiers for your own methods, variables, and classes, but you should avoid doing so if at all possible.