Книга: C# 2008 Programmer

C# Reserved Keywords

C# Reserved Keywords

The following table describes the reserved keywords used in C#.

Keyword Description
abstract A modifier that can be used with classes, methods, properties, indexers, and events. Use it to indicate that a class is intended to be used as a base class of other classes, and abstract methods must be implemented by classes that derive from the abstract class.
as An operator that performs conversion between compatible reference types.
base Used to access members of a base class from a derived class.
bool A C# alias of the System.Boolean .NET Framework type. Its value can either true, false, or null.
break Used to transfer control out of a loop or switch statement.
byte Specifies a data type that can stores unsigned 8-bit integer values from 0 to 255.
case Used together with the switch statement. It specifies the value to be matched so that control can be transferred to the case statement.
catch Used with a try block to handle one or more exceptions.
char Specifies a data type that can store a 16-bit Unicode character from U+0000 to U+ffff.
checked Used to explicitly enable overflow-checking integer operations.
class Used to declare classes.
const Used to specify a field or variable whose value cannot be modified.
continue Used within a loop such that control is transferred to the next iteration.
decimal Specifies a data type representing a 128-bit data. It can approximately represent a number from ±1.0?10-28 to ±7.9?1028.
default Used within a switch statement to indicate the default match if none of the other case statements is matched. Can also be used in generics to specify the default value of the type parameter.
delegate Used to declare a reference type variable that references a method name/anonymous method.
do Executes a block of code repeatedly until a specified expression returns false. Used together with the while keyword to form a do-while statement.
double Specifies a data type that represents a 64-bit floating point number. It can approximately represent a number from ±5.0?10-324 to ±1.7?10308.
else Used with the if keyword to form an if-else statement. else defines the block that will be executed if the expression specified in the if statement is evaluated to false.
enum Used to define an enumeration.
event Used to define an event within a class.
explicit Defines a cast operation that requires the programmer to explicitly select the cast to be performed.
extern Declares a method that is implemented externally.
false Used as either an operator or as a literal. One of the possible values in a bool variable.
finally Used in a try-catch block to contain code that cleans up the code even if an exception occurs. Statements contained within a finally block are always executed.
fixed Prevents the garbage collector from relocating a movable variable.
float Specifies a data type that represents a 32-bit floating point number. It can approximately represent a number from ±1.5?10-45 to ±3.4?1038.
for Encloses a block of statements that will be executed repeatedly until a specified expression returns false.
foreach Used to iterate through a collection of items.
goto Used to transfer control of a program to a labeled statement.
if Determines if a statement (or block of statements) is to be executed based on the result of a Boolean expression.
implicit Used to declare an implicit cast operation.
in Used in a foreach statement to specify the collection you want to iterate through.
int Specifies a data type that represents a signed 32-bit integer number. It can represent a number from -2,147,483,648 to 2,147,483,647.
interface Used to define an interface, which is a definition that contains the signatures of methods, delegates, and events. An interface does not contain any implementation.
internal An access modifier to indicate a member that can only be accessed within files in the same assembly.
is Used to check if an object is compatible with a given type.
lock Marks a statement block as a critical section so that other threads cannot execute the block while the statements within the block are being executed.
long Specifies a data type that represents a signed 64-bit integer number. It can represent a number from -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807.
namespace Used to organize your code so that it belongs to a globally unique type.
new Used to create objects and invoke a class's constructor. Also can be used to explicitly hide a base class's member in a derived class. When used in a generic declaration, it restricts types that might be used as arguments for a type declaration.
null Represents a null reference that does not refer to any object.
object A C# alias of the System.Object .NET Framework type.
operator Used to overload a built-in operator or provide a conversion operator.
out Indicates arguments that are to be passed by reference. It is similar to ref, except that ref requires the variable to be initialized before it is passed.
override Extends or modifies the abstract or virtual implementation of an inherited method, property, indexer, or event.
params Specifies a parameter array where the number of arguments is variable.
private An access modifier used to indicate a member that can only be accessed within the body of the class or struct in which it's declared.
protected An access modifier used to indicate a member that can only be accessed within its class and derived classes.
public An access modifier used to indicate a member that can be accessed by all code.
readonly A modifier that indicates fields that can only be initialized at declaration or in a constructor.
ref Indicates arguments that are to be passed by reference.
return Terminates execution of a method and returns control to the calling method.
sbyte Specifies a data type that represents a signed 8-bit integer number. It can represent a number from -128 to 127.
sealed Specifies a class that does not allow other classes to derive from it.
short Specifies a data type that represents a signed 16-bit integer number. It can represent a number from -32,768 to 32767.
sizeof Used to obtain the size in bytes for a value type.
stackalloc Used in an unsafe code context to allocate a block of memory on the stack.
static A modifier to indicate that a member belongs to the type itself, and not to a specific object.
string Specifies a data type that represents a sequence of zero or more Unicode characters. Also an alias for the System.String .NET Framework type.
struct Denotes a value type that encapsulates a group of related variables.
switch A control statement that handles multiple selections by matching the value of the switch with a series of case statements.
this Refers to the current instance of the class. Also used as a modifier of the first parameter of an extension method.
throw Used to invoke an exception during runtime.
true Used either as an operator or as a literal. One of the possible values in a bool variable.
try Indicates a block of code that may cause exceptions. Used with one or more catch blocks to handle the exceptions raised.
typeof Used to obtain the System.Type object for a type.
uint Specifies a data type that represents an unsigned 32-bit integer number. It can represent a number from 0 to 4,294,967,295.
ulong Specifies a data type that represents an unsigned 64-bit integer number. It can represent a number from 0 to 18,446,744,073,709,551,615.
unchecked Used to suppress overflow-checking for integral-type arithmetic operations and conversions.
unsafe Denotes an unsafe context, which is required for any operation involving pointers.
ushort Specifies a data type that represents an unsigned 16-bit integer number. It can represent a number from 0 to 65,535.
using A directive for creating a namespace alias or importing namespace references. It is also used for defining a scope at the end of which an object will be disposed.
virtual An access modifier to indicate a method, property, indexer, or event declaration and allow for it to be overridden in a derived class.
volatile Indicates that a field might be modified by multiple threads that are executing at the same time.
void Specifies that a method does not return any value.
while Executes a statement or a block of statements until a specified expression evaluates to false.

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