It is important that before programming you should know the C# Keywords and Identifiers. You need to know that keywords cannot be used as identifiers and more.
C# Keywords
There are some predefined and reserved words that have special meanings to the compiler. These words are called Keywords. The meaning of the keywords in C# cannot be changed nor can you use them as an identifier. Some of the keywords that you see in a program are int, float, public, etc.
For Example:
//Valid way to write keyword
int phNumber;
long cardNumber;
float @float;
//Invalid way to write keyword
int int;
float double;There are 79 keywords in C#. All the keywords are written in lowercase.
List of C# keywords
| 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 |
Contextual Keywords
Aside from the above keywords, C# has 25 other keywords which are called contextual keywords. They have some specific meaning in a program. Unlike the above 79 regular keywords, contextual keywords are not reserved, they can be used as an identifier.
| 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 |
You may go through each of them, Click Here.
C# Identifiers
Identifiers are nothing but the name assigned to the entities such as variables, functions in a program, Union, classes, etc. They are tokens that has a unique name so that they can be uniquely identified in a program.
Example: int number;, number being an identifier.
Rules for Naming an Identifiers:
- Identifiers are case-sensitive that is uppercase and lowercase letters are distinct.
- The first letter of identifiers must be a letter or underscore or symbols. After the first letter, you can use digits.
- White spaces are not allowed.
- A keyword cannot be used as an identifier.
Some valid and invalid identifiers:
//Valid
Number
result1
_multiply
S2C
@number
@int
//Invalid
Number-2 //special character '-' is present.
3Sum //started with digit
int // int is a keyword