System namespace

The System namespace contains fundamental classes and base classes that define commonly used value and reference data types, events and event handlers, interfaces, attributes, and processing exceptions.

This topic displays the types in the System namespace that are included in the .NET for Windows Store apps. Note that the .NET for Windows Store apps does not include all the members of each type. For information about individual types, see the linked topics. The documentation for a type indicates which members are included in the .NET for Windows Store apps.

Types supported in the .NET for Windows Store apps

Description

Action

Encapsulates a method that has no parameters and does not return a value.

Action<T>

Encapsulates a method that has a single parameter and does not return a value.

Action<T1, T2>

Encapsulates a method that has two parameters and does not return a value.

Action<T1, T2, T3>

Encapsulates a method that has three parameters and does not return a value.

Action<T1, T2, T3, T4>

Encapsulates a method that has four parameters and does not return a value.

Action<T1, T2, T3, T4, T5>

Encapsulates a method that has five parameters and does not return a value.

Action<T1, T2, T3, T4, T5, T6>

Encapsulates a method that has six parameters and does not return a value.

Action<T1, T2, T3, T4, T5, T6, T7>

Encapsulates a method that has seven parameters and does not return a value.

Action<T1, T2, T3, T4, T5, T6, T7, T8>

Encapsulates a method that has eight parameters and does not return a value.

Action<T1, T2, T3, T4, T5, T6, T7, T8, T9>

Encapsulates a method that has nine parameters and does not return a value.

Action<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10>

Encapsulates a method that has ten parameters and does not return a value.

Action<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11>

Encapsulates a method that has eleven parameters and does not return a value.

Action<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12>

Encapsulates a method that has twelve parameters and does not return a value.

Action<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13>

Encapsulates a method that has thirteen parameters and does not return a value.

Action<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14>

Encapsulates a method that has fourteen parameters and does not return a value.

Action<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15>

Encapsulates a method that has fifteen parameters and does not return a value.

Action<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16>

Encapsulates a method that has sixteen parameters and does not return a value.

Activator

Contains methods to create types of objects locally or remotely, or obtain references to existing remote objects. This class cannot be inherited.

AggregateException

Represents one or more errors that occur during application execution.

ArgumentException

The exception that is thrown when one of the arguments provided to a method is not valid.

ArgumentNullException

The exception that is thrown when a null reference is passed to a method that does not accept it as a valid argument.

ArgumentOutOfRangeException

The exception that is thrown when the value of an argument is outside the allowable range of values as defined by the invoked method.

ArithmeticException

The exception that is thrown for errors in an arithmetic, casting, or conversion operation.

Array

Provides methods for creating, manipulating, searching, and sorting arrays, thereby serving as the base class for all arrays in the common language runtime.

ArraySegment<T>

Delimits a section of a one-dimensional array.

ArrayTypeMismatchException

The exception that is thrown when an attempt is made to store an element of the wrong type within an array.

AsyncCallback

References a method to be called when a corresponding asynchronous operation completes.

Attribute

Represents the base class for custom attributes.

AttributeTargets

Specifies the application elements on which it is valid to apply an attribute.

AttributeUsageAttribute

Specifies the usage of another attribute class. This class cannot be inherited.

BadImageFormatException

The exception that is thrown when the file image of a dynamic link library (DLL) or an executable program is invalid.

BitConverter

Converts base data types to an array of bytes, and an array of bytes to base data types.

Boolean

Represents a Boolean value.

Buffer

Manipulates arrays of primitive types.

Byte

Represents an 8-bit unsigned integer.

Char

Represents a Unicode character.

CLSCompliantAttribute

Indicates whether a program element is compliant with the Common Language Specification (CLS). This class cannot be inherited.

Comparison<T>

Represents the method that compares two objects of the same type.

Convert

Converts a base data type to another base data type.

DataMisalignedException

The exception that is thrown when a unit of data is read from or written to an address that is not a multiple of the data size. This class cannot be inherited.

DateTime

Represents an instant in time, typically expressed as a date and time of day.

DateTimeKind

Specifies whether a DateTime object represents a local time, a Coordinated Universal Time (UTC), or is not specified as either local time or UTC.

DateTimeOffset

Represents a point in time, typically expressed as a date and time of day, relative to Coordinated Universal Time (UTC).

DayOfWeek

Specifies the day of the week.

Decimal

Represents a decimal number.

Delegate

Represents a delegate, which is a data structure that refers to a static method or to a class instance and an instance method of that class.

DivideByZeroException

The exception that is thrown when there is an attempt to divide an integral or decimal value by zero.

DllNotFoundException

The exception that is thrown when a DLL specified in a DLL import cannot be found.

Double

Represents a double-precision floating-point number.

Enum

Provides the base class for enumerations.

Environment

Provides information about, and means to manipulate, the current environment and platform. This class cannot be inherited.

EventArgs

Represents the base class for classes that contain event data.

EventHandler

Represents the method that will handle an event that has no event data.

EventHandler<TEventArgs>

Represents the method that will handle an event.

Exception

Represents errors that occur during application execution.

FlagsAttribute

Indicates that an enumeration can be treated as a bit field; that is, a set of flags.

FormatException

The exception that is thrown when the format of an argument does not meet the parameter specifications of the invoked method.

Func<TResult>

Encapsulates a method that has no parameters and returns a value of the type specified by the TResult parameter.

Func<T, TResult>

Encapsulates a method that has one parameter and returns a value of the type specified by the TResult parameter.

Func<T1, T2, TResult>

Encapsulates a method that has two parameters and returns a value of the type specified by the TResult parameter.

Func<T1, T2, T3, TResult>

Encapsulates a method that has three parameters and returns a value of the type specified by the TResult parameter.

Func<T1, T2, T3, T4, TResult>

Encapsulates a method that has four parameters and returns a value of the type specified by the TResult parameter.

Func<T1, T2, T3, T4, T5, TResult>

Encapsulates a method that has five parameters and returns a value of the type specified by the TResult parameter.

Func<T1, T2, T3, T4, T5, T6, TResult>

Encapsulates a method that has six parameters and returns a value of the type specified by the TResult parameter.

Func<T1, T2, T3, T4, T5, T6, T7, TResult>

Encapsulates a method that has seven parameters and returns a value of the type specified by the TResult parameter.

Func<T1, T2, T3, T4, T5, T6, T7, T8, TResult>

Encapsulates a method that has eight parameters and returns a value of the type specified by the TResult parameter.

Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, TResult>

Encapsulates a method that has nine parameters and returns a value of the type specified by the TResult parameter.

Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, TResult>

Encapsulates a method that has ten parameters and returns a value of the type specified by the TResult parameter.

Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, TResult>

Encapsulates a method that has eleven parameters and returns a value of the type specified by the TResult parameter.

Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, TResult>

Encapsulates a method that has twelve parameters and returns a value of the type specified by the TResult parameter.

Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, TResult>

Encapsulates a method that has thirteen parameters and returns a value of the type specified by the TResult parameter.

Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, TResult>

Encapsulates a method that has fourteen parameters and returns a value of the type specified by the TResult parameter.

Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, TResult>

Encapsulates a method that has fifteen parameters and returns a value of the type specified by the TResult parameter.

GC

Controls the system garbage collector, which is a service that automatically reclaims unused memory.

GCCollectionMode

Specifies the behavior for a forced garbage collection.

Guid

Represents a globally unique identifier (GUID).

IAsyncResult

Represents the status of an asynchronous operation.

IComparable

Defines a generalized type-specific comparison method that a value type or class implements to order or sort its instances.

IComparable<T>

Defines a generalized comparison method that a value type or class implements to create a type-specific comparison method for ordering instances.

ICustomFormatter

Defines a method that supports custom formatting of the value of an object.

IDisposable

Defines a method to release allocated resources.

IEquatable<T>

Defines a generalized method that a value type or class implements to create a type-specific method for determining equality of instances.

IFormatProvider

Provides a mechanism for retrieving an object to control formatting.

IFormattable

Provides functionality to format the value of an object into a string representation.

IndexOutOfRangeException

The exception that is thrown when an attempt is made to access an element of an array with an index that is outside the bounds of the array. This class cannot be inherited.

Int16

Represents a 16-bit signed integer.

Int32

Represents a 32-bit signed integer.

Int64

Represents a 64-bit signed integer.

IntPtr

A platform-specific type that is used to represent a pointer or a handle.

InvalidCastException

The exception that is thrown for invalid casting or explicit conversion.

InvalidOperationException

The exception that is thrown when a method call is invalid for the object's current state.

InvalidTimeZoneException

The exception that is thrown when time zone information is invalid.

IObservable<T>

Defines a provider for push-based notification.

IObserver<T>

Provides a mechanism for receiving push-based notifications.

IProgress<T>

Defines a provider for progress updates.

IServiceProvider

Defines a mechanism for retrieving a service object; that is, an object that provides custom support to other objects.

Lazy<T>

Provides support for lazy initialization.

Lazy<T, TMetadata>

Provides a lazy indirect reference to an object and its associated metadata for use by the Managed Extensibility Framework.

Math

Provides constants and static methods for trigonometric, logarithmic, and other common mathematical functions.

MemberAccessException

The exception that is thrown when an attempt to access a class member fails.

MidpointRounding

Specifies how mathematical rounding methods should process a number that is midway between two numbers.

MissingMemberException

The exception that is thrown when there is an attempt to dynamically access a class member that does not exist.

MTAThreadAttribute

Indicates that the COM threading model for an application is multithreaded apartment (MTA).

MulticastDelegate

Represents a multicast delegate; that is, a delegate that can have more than one element in its invocation list.

NotImplementedException

The exception that is thrown when a requested method or operation is not implemented.

NotSupportedException

The exception that is thrown when an invoked method is not supported, or when there is an attempt to read, seek, or write to a stream that does not support the invoked functionality.

Nullable

Supports a value type that can be assigned null like a reference type. This class cannot be inherited.

Nullable<T>

Represents an object whose underlying type is a value type that can also be assigned null like a reference type.

NullReferenceException

The exception that is thrown when there is an attempt to dereference a null object reference.

Object

Supports all classes in the .NET Framework class hierarchy and provides low-level services to derived classes. This is the ultimate base class of all classes in the .NET Framework; it is the root of the type hierarchy.

ObjectDisposedException

The exception that is thrown when an operation is performed on a disposed object.

ObsoleteAttribute

Marks the program elements that are no longer in use. This class cannot be inherited.

OperationCanceledException

The exception that is thrown in a thread upon cancellation of an operation that the thread was executing.

OutOfMemoryException

The exception that is thrown when there is not enough memory to continue the execution of a program.

OverflowException

The exception that is thrown when an arithmetic, casting, or conversion operation in a checked context results in an overflow.

ParamArrayAttribute

Indicates that a method will allow a variable number of arguments in its invocation. This class cannot be inherited.

PlatformNotSupportedException

The exception that is thrown when a feature does not run on a particular platform.

Predicate<T>

Represents the method that defines a set of criteria and determines whether the specified object meets those criteria.

Progress<T>

Provides an IProgress<T> that invokes callbacks for each reported progress value.

Random

Represents a pseudo-random number generator, a device that produces a sequence of numbers that meet certain statistical requirements for randomness.

RankException

The exception that is thrown when an array with the wrong number of dimensions is passed to a method.

RuntimeFieldHandle

Represents a field using an internal metadata token.

RuntimeMethodHandle

Provides a handle to the internal metadata representation of a method.

RuntimeTypeHandle

Represents a type using an internal metadata token.

SByte

Represents an 8-bit signed integer.

Single

Represents a single-precision floating-point number.

STAThreadAttribute

Indicates that the COM threading model for an application is single-threaded apartment (STA).

String

Represents text as a series of Unicode characters.

StringComparer

Represents a string comparison operation that uses specific case and culture-based or ordinal comparison rules.

StringComparison

Specifies the culture, case, and sort rules to be used by certain overloads of the Compare and Equals methods.

StringSplitOptions

Specifies whether applicable Split method overloads include or omit empty substrings from the return value.

ThreadStaticAttribute

Indicates that the value of a static field is unique for each thread.

TimeoutException

The exception that is thrown when the time allotted for a process or operation has expired.

TimeSpan

Represents a time interval.

TimeZoneInfo

Represents any time zone in the world.

Tuple

Provides static methods for creating tuple objects.

Tuple<T1>

Represents a 1-tuple, or singleton.

Tuple<T1, T2>

Represents a 2-tuple, or pair.

Tuple<T1, T2, T3>

Represents a 3-tuple, or triple.

Tuple<T1, T2, T3, T4>

Represents a 4-tuple, or quadruple.

Tuple<T1, T2, T3, T4, T5>

Represents a 5-tuple, or quintuple.

Tuple<T1, T2, T3, T4, T5, T6>

Represents a 6-tuple, or sextuple.

Tuple<T1, T2, T3, T4, T5, T6, T7>

Represents a 7-tuple, or septuple.

Tuple<T1, T2, T3, T4, T5, T6, T7, TRest>

Represents an n-tuple, where n is 8 or greater.

Type

Represents type declarations: class types, interface types, array types, value types, enumeration types, type parameters, generic type definitions, and open or closed constructed generic types.

TypeAccessException

The exception that is thrown when a method attempts to use a type that it does not have access to.

TypeInitializationException

The exception that is thrown as a wrapper around the exception thrown by the class initializer. This class cannot be inherited.

TypeLoadException

The exception that is thrown when type-loading failures occur.

UInt16

Represents a 16-bit unsigned integer.

UInt32

Represents a 32-bit unsigned integer.

UInt64

Represents a 64-bit unsigned integer.

UIntPtr

A platform-specific type that is used to represent a pointer or a handle.

UnauthorizedAccessException

The exception that is thrown when the operating system denies access because of an I/O error or a specific type of security error.

Uri

Provides an object representation of a uniform resource identifier (URI) and easy access to the parts of the URI.

UriBuilder

Provides a custom constructor for uniform resource identifiers (URIs) and modifies URIs for the System.Uri class.

UriComponents

Specifies the parts of a Uri.

UriFormat

Controls how URI information is escaped.

UriHostNameType

Defines host name types for the CheckHostName method.

UriKind

Defines the kinds of URIs for the IsWellFormedUriString and several URI constructor methods.

ValueType

Provides the base class for value types.

Version

Represents the version number of an assembly, operating system, or the common language runtime. This class cannot be inherited.

Void

Specifies a return value type for a method that does not return a value.

WeakReference

Represents a weak reference, which references an object while still allowing that object to be reclaimed by garbage collection.

WeakReference<T>

Represents a typed weak reference, which references an object while still allowing that object to be reclaimed by garbage collection.

WindowsRuntimeSystemExtensions

Provides extension methods for working with the Windows Runtime.

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