Types of Keywords in C#

C# contain reserved words that have special meaning for the compiler. the words which are reserved by C# are known as C# Keywords. These words can not be used as the name of the variable, name of the interface, name of the class, etc.

C# keywords or distributed in the following categories.

Modifiers
Access modifiers
Statement
Method Parameter
Operator
Namespace
Access
Literal
Type
Query
Contextual

Modifiers Keywords

Modifier keywords are those keywords that indicate modify the type and type members. These keywords allow are to prevent certain parts of a program from being modified by another part below are modifiers keyword.

Modifiers Keywords	Description
`abstract`	If a class marked with abstract it's mean this class can only be intended to be a base class of others
`async`	The async keyword indicates that the method is asynchronous
`const`	The keyword indicates that the value of the variable can not be modified
`event`	This keyword used for the declaration of an event
`extern`	For the external implementation of the method
`new`	This keyword explicitly hides the member
`override`	This keyword provides the new implementation of the virtual member
`partial`	This is used for the declaration of the partial class
`readonly`	This keyword indicates that the field can only be assigned as a part of the declaration
`sealed`	If a class marked with sealed it means that class can not be inherited
`static`	A member that itself belongs to a type
`unsafe`	For the declaration of unsafe context
`virtual`	Indicate that the implementation can be changed by an override method
`volatile`	Indicate that a field cannot be modified in a program

Access modifiers

Access modifiers are defined at the stage of the declaration of a class, method, properties, or members. these keywords define the accessibility of the class and its member.

For a class or struct, the default access modifier is private and for the interface and enum is public.

You can find some access modifiers from the below table

Access modifiers	Description
`Public`	Access is not limited to a type or type member. This keyword provides complete visibility.
`Private`	Default access modifier type. Access is limited only code in the same class or struct can access it
`Protected`	limited access to the containing type or types derived from the containing class
`Internal`	Limited access to the current assembly only

Statement Keyword

Basically, keywords under this category are program instructions. these keywords are executed in sequence. The below table lists the C# statement keywords.

Statement Keyword
`if`
`else`
`switch`
`case`
`do`
`for`
`foreach`
`in`
`while`
`break`
`continue`
`default`
`goto`
`return`
`yield`
`throw`
`try`
`catch`
`finally`
`checked`
`unchecked`
`fixed`
`lock`

statement keywords further divide into the following categories.

Category	C# Keywords
Selection statement	`if,else,switch,case`
itteration statement	`do, for,foreach,while,in`
jump statement	`break, continue, default, goto, return, yield`
exception handling	`throw, try catch, try-finally, try-finally-catch`
checked and unchecked	`checked, unchecked`
fixed statement	`fixed`
lock statement	`lock`

Method Parameter

Those keywords are applied as the parameter of the method

Method Parameter
`params`
`ref`
`out`

Namespace Keywords

Those keywords are applied with the namespace. Within a namespace, we can define more of the following types.

Using
. operator
:: operator
extern alias

Operator Keyword

C# provides operator keywords a number of them support built-in types and allow us to perform operations. Which are listed below the table.

Operator Keyword	Description
`as`	The conversion of an object into the compatible type
`await`	The suspension of asynchronous function to compute the await task
`is`	This keyword checks the type of an object during the run time.
`new`	The creation of a new object, or for the hides an inherited member.
`sizeof`	This keyword uses to obtain the size of a given object.
`typeof`	Returns the system.type of object.
`stackalloc`	The allocation of the block of memory.
`checked`	This keyword is used to explicitly enable overflow checking for integral-type arithmetic operations and conversions
`unchecked`	This keyword is used to suppress overflow-checking for integral-type arithmetic operations and conversions

Access Keywords

Access keywords are used to access the containing class or the base class of an object or class.

Access Keywords
`base`
`this`

Literal Keywords

Literal keywords apply to the current instance or value of an object.

Literal Keywords
`null`
`false`
`true`
`value`
`void`

Type Keywords

Type keywords are used for data types.

Type Keywords
`bool`
`byte`
`char`
`class`
`decimal`
`double`
`enum`
`float`
`int`
`long`
`sbyte`
`short`
`string`
`struct`
`uint`
`ulong`
`ushort`

Contextual Keywords

Contextual keywords are considered as keywords, only if used in specific contexts. They are not reserved and so can be used as names or identifiers.

These keywords cannot be converted into the default keyword colors which is blue when we use them in c# as an identifier.

Contextual Keywords
`add`
`var`
`dynamic`
`global`
`set`
`value`

Query Keywords

Query keywords are contextual keywords used in query expressions.

Query Keywords	Description
`from`	define the range of a variable or data source
`where`	filter the element in the boolean expression.
`select`	return sequence
`group`	a specified group query result according to a specified key-value
`into`	an identifier that can serve as a reference to the results of a join, group or select clause
`orderby`	ascending or descending order of the return result
`join`	for the join of the data source
`let`	the range of the variable
`in`	a keyword in the join clause
`on`	a keyword in the join clause
`equals`	a keyword in the join clause
`by`	a keyword in the group clause
`ascending`	a keyword in an orderby clause
`descending`	a keyword in an orderby clause