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.

System namespace

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.

See Also

Concepts

.NET for Windows Store apps - supported APIs