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System Namespace

July 28, 2014

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.

Other classes provide services supporting data type conversion, method parameter manipulation, mathematics, remote and local program invocation, application environment management, and supervision of managed and unmanaged applications.

  ClassDescription
Public classAccessViolationExceptionThe exception that is thrown when there is an attempt to read or write protected memory.
Public classActivatorContains methods to create types of objects locally. This class cannot be inherited.
Public classAggregateExceptionRepresents one or more errors that occur during application execution.
Public classAppDomainRepresents an application domain, which is an isolated environment where applications execute. This class cannot be inherited.
Public classAppDomainManagerProvides a managed equivalent of an unmanaged host.
Public classAppDomainSetupRepresents assembly binding information that can be added to an instance of AppDomain.
Public classAppDomainUnloadedExceptionThe exception that is thrown when an attempt is made to access an unloaded application domain.
Public classApplicationExceptionThe exception that is thrown when a non-fatal application error occurs.
Public classArgumentExceptionThe exception that is thrown when one of the arguments provided to a method is not valid.
Public classArgumentNullExceptionThe exception that is thrown when a null reference (Nothing in Visual Basic) is passed to a method that does not accept it as a valid argument.
Public classArgumentOutOfRangeExceptionThe exception that is thrown when the value of an argument is outside the allowable range of values as defined by the invoked method.
Public classArithmeticExceptionThe exception that is thrown for errors in an arithmetic, casting, or conversion operation.
Public classArrayProvides methods for creating, manipulating, searching, and sorting arrays, thereby serving as the base class for all arrays in the common language runtime.
Public classArrayTypeMismatchExceptionThe exception that is thrown when an attempt is made to store an element of the wrong type within an array.
Public classAttributeRepresents the base class for custom attributes.
Public classAttributeUsageAttributeSpecifies the usage of another attribute class. This class cannot be inherited.
Public classBadImageFormatExceptionThe exception that is thrown when the file image of a DLL or an executable program is invalid.
Public classBitConverterConverts base data types to an array of bytes, and an array of bytes to base data types.
Public classBufferManipulates arrays of primitive types.
Public classCannotUnloadAppDomainExceptionThe exception that is thrown when an attempt to unload an application domain fails.
Public classCLSCompliantAttributeIndicates whether a program element is compliant with the Common Language Specification (CLS). This class cannot be inherited.
Public classConsoleInfrastructure. Represents the standard input, output, and error streams for console applications. This class cannot be inherited.
Public classContextStaticAttribute Obsolete. Indicates that the value of a static field is unique for a particular context.
Public classConvertConverts a base data type to another base data type.
Public classDataMisalignedExceptionThe 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.
Public classDBNullRepresents a nonexistent value. This class cannot be inherited.
Public classDelegateRepresents 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.
Public classDivideByZeroExceptionThe exception that is thrown when there is an attempt to divide an integral or decimal value by zero.
Public classDllNotFoundExceptionThe exception that is thrown when a DLL specified in a DLL import cannot be found.
Public classEntryPointNotFoundExceptionThe exception that is thrown when an attempt to load a class fails due to the absence of an entry method.
Public classEnumProvides the base class for enumerations.
Public classEnvironmentProvides information about, and means to manipulate, the current environment and platform. This class cannot be inherited.
Public classEventArgsEventArgs is the base class for classes containing event data.
Public classExceptionRepresents errors that occur during application execution.
Public classExecutionEngineException Obsolete. The exception that is thrown when there is an internal error in the execution engine of the common language runtime. This class cannot be inherited.
Public classFieldAccessExceptionThe exception that is thrown when there is an invalid attempt to access a private or protected field inside a class.
Public classFileStyleUriParserA customizable parser based on the File scheme.
Public classFlagsAttributeIndicates that an enumeration can be treated as a bit field; that is, a set of flags.
Public classFormatExceptionThe exception that is thrown when the format of an argument does not meet the parameter specifications of the invoked method.
Public classFtpStyleUriParserA customizable parser based on the File Transfer Protocol (FTP) scheme.
Public classGCControls the system garbage collector, a service that automatically reclaims unused memory.
Public classGenericUriParserA customizable parser for a hierarchical URI.
Public classHttpStyleUriParserA customizable parser based on the HTTP scheme.
Public classIndexOutOfRangeExceptionThe 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.
Public classInvalidCastExceptionThe exception that is thrown for invalid casting or explicit conversion.
Public classInvalidOperationExceptionThe exception that is thrown when a method call is invalid for the object's current state.
Public classInvalidProgramExceptionThe exception that is thrown when a program contains invalid Microsoft intermediate language (MSIL) or metadata. Generally this indicates a bug in the compiler that generated the program.
Public classInvalidTimeZoneExceptionThe exception that is thrown when time zone information is invalid.
Public classLazy<T>Provides support for lazy initialization.
Public classLazy<T, TMetadata>Provides an extension of the Lazy<T> class with support for metadata.
Public classMathProvides constants and static methods for trigonometric, logarithmic, and other common mathematical functions.
Public classMemberAccessExceptionThe exception that is thrown when an attempt to access a class member fails.
Public classMethodAccessExceptionThe exception that is thrown when there is an invalid attempt to access a private or protected method inside a class.
Public classMissingFieldExceptionThe exception that is thrown when there is an attempt to dynamically access a field that does not exist.
Public classMissingMemberExceptionThe exception that is thrown when there is an attempt to dynamically access a class member that does not exist.
Public classMissingMethodExceptionThe exception that is thrown when there is an attempt to dynamically access a method that does not exist.
Public classMTAThreadAttributeIndicates that the COM threading model for an application is multithreaded apartment (MTA).
Public classMulticastDelegateRepresents a multicast delegate; that is, a delegate that can have more than one element in its invocation list.
Public classMulticastNotSupportedExceptionThe exception that is thrown when there is an attempt to combine two delegates based on the Delegate type instead of the MulticastDelegate type. This class cannot be inherited.
Public classNotFiniteNumberExceptionThe exception that is thrown when a floating-point value is positive infinity, negative infinity, or Not-a-Number (NaN).
Public classNotImplementedExceptionThe exception that is thrown when a requested method or operation is not implemented.
Public classNotSupportedExceptionThe 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.
Public classNullableSupports a value type that can be assigned null like a reference type. This class cannot be inherited.
Public classNullReferenceExceptionThe exception that is thrown when there is an attempt to dereference a null object reference.
Public classObjectSupports 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.
Public classObjectDisposedExceptionThe exception that is thrown when an operation is performed on a disposed object.
Public classObsoleteAttributeMarks the program elements that are no longer in use. This class cannot be inherited.
Public classOperatingSystemRepresents information about an operating system, such as the version and platform identifier. This class cannot be inherited.
Public classOperationCanceledExceptionThe exception that is thrown in a thread upon cancellation of an operation that the thread was executing.
Public classOutOfMemoryExceptionThe exception that is thrown when there is not enough memory to continue the execution of a program.
Public classOverflowExceptionThe exception that is thrown when an arithmetic, casting, or conversion operation in a checked context results in an overflow.
Public classParamArrayAttributeIndicates that a method will allow a variable number of arguments in its invocation. This class cannot be inherited.
Public classPlatformNotSupportedExceptionThe exception that is thrown when a feature does not run on a particular platform.
Public classProgress<T>Provides an IProgress<T> that invokes callbacks for each reported progress value.
Public classRandomRepresents a pseudo-random number generator, a device that produces a sequence of numbers that meet certain statistical requirements for randomness.
Public classRankExceptionThe exception that is thrown when an array with the wrong number of dimensions is passed to a method.
Public classResolveEventArgsProvides data for the event that resolves assembly loads. Not supported in Windows Phone apps.
Public classStackOverflowExceptionThe exception that is thrown when the execution stack overflows because it contains too many nested method calls. This class cannot be inherited.
Public classSTAThreadAttributeIndicates that the COM threading model for an application is single-threaded apartment (STA).
Public classStringRepresents text as a series of Unicode characters.
Public classStringComparerRepresents a string comparison operation that uses specific case and culture-based or ordinal comparison rules.
Public classSystemExceptionDefines the base class for predefined exceptions in the System namespace.
Public classThreadStaticAttributeIndicates that the value of a static field is unique for each thread.
Public classTimeoutExceptionThe exception that is thrown when the time allotted for a process or operation has expired.
Public classTimeZoneInfoRepresents a time zone.
Public classTupleProvides static methods for creating tuple objects.
Public classTuple<T1>Represents a 1-tuple, or singleton.
Public classTuple<T1, T2>Represents a 2-tuple, or pair.
Public classTuple<T1, T2, T3>Represents a 3-tuple, or triple.
Public classTuple<T1, T2, T3, T4>Represents a 4-tuple, or quadruple.
Public classTuple<T1, T2, T3, T4, T5>Represents a 5-tuple, or quintuple.
Public classTuple<T1, T2, T3, T4, T5, T6>Represents a 6-tuple, or sextuple.
Public classTuple<T1, T2, T3, T4, T5, T6, T7>Represents a 7-tuple, or septuple.
Public classTuple<T1, T2, T3, T4, T5, T6, T7, TRest>Represents an n-tuple, where n is 8 or greater.
Public classTypeRepresents type declarations: class types, interface types, array types, value types, enumeration types, type parameters, generic type definitions, and open or closed constructed generic types.
Public classTypeAccessExceptionThe exception that is thrown when a method attempts to use a type that it does not have access to.
Public classTypeInitializationExceptionThe exception that is thrown as a wrapper around the exception thrown by the class initializer. This class cannot be inherited.
Public classTypeLoadExceptionThe exception that is thrown when type-loading failures occur.
Public classUnauthorizedAccessExceptionThe exception that is thrown when the operating system denies access because of an I/O error or a specific type of security error.
Public classUnhandledExceptionEventArgsProvides data for the event that is raised when there is an exception that is not handled in any application domain.
Public classUriProvides an object representation of a uniform resource identifier (URI) and easy access to the parts of the URI.
Public classUriBuilderProvides a custom constructor for uniform resource identifiers (URIs) and modifies URIs for the Uri class.
Public classUriFormatExceptionThe exception that is thrown when an invalid Uniform Resource Identifier (URI) is detected.
Public classUriParserParses a new URI scheme. This is an abstract class.
Public classUriTypeConverterConverts instances of the String type to Uri instances.
Public classValueTypeProvides the base class for value types.
Public classVersionRepresents the version number of an assembly, operating system, or the common language runtime. This class cannot be inherited.
Public classWeakReferenceRepresents a weak reference, which references an object while still allowing that object to be reclaimed by garbage collection.
Public classWeakReference<T>Represents a typed weak reference, which references an object while still allowing that object to be reclaimed by garbage collection.
Public classWindowsRuntimeSystemExtensionsProvides extension methods for converting between tasks and Windows Runtime asynchronous actions and operations.

  StructureDescription
Public structureArraySegment<T>Delimits a section of a one-dimensional array.
Public structureBooleanRepresents a Boolean value.
Public structureByteRepresents an 8-bit unsigned integer.
Public structureCharRepresents a Unicode character.
Public structureDateTimeRepresents an instant in time, typically expressed as a date and time of day.
Public structureDateTimeOffsetRepresents a point in time, typically expressed as a date and time of day, relative to Coordinated Universal Time (UTC).
Public structureDecimalRepresents a decimal number.
Public structureDoubleRepresents a double-precision floating-point number.
Public structureGuidRepresents a globally unique identifier (GUID).
Public structureInt16Represents a 16-bit signed integer.
Public structureInt32Represents a 32-bit signed integer.
Public structureInt64Represents a 64-bit signed integer.
Public structureIntPtrA platform-specific type that is used to represent a pointer or a handle.
Public structureNullable<T>Represents an object whose underlying type is a value type that can also be assigned null like a reference type.
Public structureRuntimeArgumentHandleReferences a variable-length argument list.
Public structureRuntimeFieldHandleRepresents a field using an internal metadata token.
Public structureRuntimeMethodHandleRuntimeMethodHandle is a handle to the internal metadata representation of a method.
Public structureRuntimeTypeHandleRepresents a type using an internal metadata token.
Public structureSByteRepresents an 8-bit signed integer.
Public structureSingleRepresents a single-precision floating-point number.
Public structureTimeSpanRepresents a time interval.
Public structureUInt16Represents a 16-bit unsigned integer.
Public structureUInt32Represents a 32-bit unsigned integer.
Public structureUInt64Represents a 64-bit unsigned integer.
Public structureUIntPtrA platform-specific type that is used to represent a pointer or a handle.
Public structureVoidSpecifies a return value type for a method that does not return a value.

  InterfaceDescription
Public interfaceIAsyncResultRepresents the status of an asynchronous operation.
Public interfaceIComparableDefines a generalized type-specific comparison method that a value type or class implements to order or sort its instances.
Public interfaceIComparable<T>Defines a generalized comparison method that a value type or class implements to create a type-specific comparison method for ordering instances.
Public interfaceIConvertibleDefines methods that convert the value of the implementing reference or value type to a common language runtime type that has an equivalent value.
Public interfaceICustomFormatterDefines a method that supports custom, user-defined formatting of the value of an object.
Public interfaceIDisposableDefines a method to release allocated resources.
Public interfaceIEquatable<T>Defines a generalized method that a value type or class implements to create a type-specific method for determining equality of instances.
Public interfaceIFormatProviderProvides a mechanism for retrieving an object to control formatting.
Public interfaceIFormattableProvides functionality to format the value of an object into a string representation.
Public interfaceIObservable<T>Defines a provider for push-based notification.
Public interfaceIObserver<T>Provides a mechanism for receiving push-based notifications.
Public interfaceIProgress<T>Defines a provider for progress updates.
Public interfaceIServiceProviderDefines a mechanism for retrieving a service object; that is, an object that provides custom support to other objects.

  DelegateDescription
Public delegateActionEncapsulates a method that takes no parameters and does not return a value.
Public delegateAction<T>Encapsulates a method that takes a single parameter and does not return a value.
Public delegateAction<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10>Encapsulates a method that has 10 parameters and does not return a value.
Public delegateAction<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11>Encapsulates a method that has 11 parameters and does not return a value.
Public delegateAction<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12>Encapsulates a method that has 12 parameters and does not return a value.
Public delegateAction<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13>Encapsulates a method that has 13 parameters and does not return a value.
Public delegateAction<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14>Encapsulates a method that has 14 parameters and does not return a value.
Public delegateAction<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15>Encapsulates a method that has 15 parameters and does not return a value.
Public delegateAction<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16>Encapsulates a method that has 16 parameters and does not return a value.
Public delegateAction<T1, T2>Encapsulates a method that has two parameters and does not return a value.
Public delegateAction<T1, T2, T3>Encapsulates a method that takes three parameters and does not return a value.
Public delegateAction<T1, T2, T3, T4>Encapsulates a method that has four parameters and does not return a value.
Public delegateAction<T1, T2, T3, T4, T5>Encapsulates a method that has five parameters and does not return a value.
Public delegateAction<T1, T2, T3, T4, T5, T6>Encapsulates a method that has six parameters and does not return a value.
Public delegateAction<T1, T2, T3, T4, T5, T6, T7>Encapsulates a method that has seven parameters and does not return a value.
Public delegateAction<T1, T2, T3, T4, T5, T6, T7, T8>Encapsulates a method that has eight parameters and does not return a value.
Public delegateAction<T1, T2, T3, T4, T5, T6, T7, T8, T9>Encapsulates a method that has nine parameters and does not return a value.
Public delegateAsyncCallbackReferences a method to be called when a corresponding asynchronous operation is completed.
Public delegateComparison<T>Represents the method that compares two objects of the same type.
Public delegateConverter<TInput, TOutput>Represents a method that converts an object from one type to another type.
Public delegateEventHandlerRepresents the method that will handle an event that has no event data.
Public delegateEventHandler<TEventArgs>Represents the method that will handle an event.
Public delegateFunc<TResult>Encapsulates a method that has no parameters and returns a value of the type specified by the TResult parameter.
Public delegateFunc<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.
Public delegateFunc<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, TResult>Encapsulates a method that has 10 parameters and returns a value of the type specified by the TResult parameter.
Public delegateFunc<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, TResult>Encapsulates a method that has 11 parameters and returns a value of the type specified by the TResult parameter.
Public delegateFunc<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, TResult>Encapsulates a method that has 12 parameters and returns a value of the type specified by the TResult parameter.
Public delegateFunc<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, TResult>Encapsulates a method that has 13 parameters and returns a value of the type specified by the TResult parameter.
Public delegateFunc<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, TResult>Encapsulates a method that has 14 parameters and returns a value of the type specified by the TResult parameter.
Public delegateFunc<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, TResult>Encapsulates a method that has 15 parameters and returns a value of the type specified by the TResult parameter.
Public delegateFunc<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, TResult>Encapsulates a method that has 16 parameters and returns a value of the type specified by the TResult parameter.
Public delegateFunc<T, TResult>Encapsulates a method that has one parameter and returns a value of the type specified by the TResult parameter.
Public delegateFunc<T1, T2, TResult>Encapsulates a method that has two parameters and returns a value of the type specified by the TResult parameter.
Public delegateFunc<T1, T2, T3, TResult>Encapsulates a method that has three parameters and returns a value of the type specified by the TResult parameter.
Public delegateFunc<T1, T2, T3, T4, TResult>Encapsulates a method that has four parameters and returns a value of the type specified by the TResult parameter.
Public delegateFunc<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.
Public delegateFunc<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.
Public delegateFunc<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.
Public delegateFunc<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.
Public delegatePredicate<T>Represents the method that defines a set of criteria and determines whether the specified object meets those criteria.
Public delegateResolveEventHandlerRepresents the method that handles the event that resolves assembly loads. Not supported in Windows Phone.
Public delegateUnhandledExceptionEventHandlerRepresents the method that will handle the event raised by an exception that is not handled by the application domain.

  EnumerationDescription
Public enumerationAttributeTargetsSpecifies the application elements on which it is valid to apply an attribute.
Public enumerationDateTimeKindSpecifies whether a DateTime object represents a local time, a Coordinated Universal Time (UTC), or is not specified as either local time or UTC.
Public enumerationDayOfWeekSpecifies the day of the week.
Public enumerationEnvironment.SpecialFolderSpecifies enumerated constants used to retrieve directory paths to system special folders.
Public enumerationGCCollectionModeSpecifies the behavior for a forced garbage collection.
Public enumerationGenericUriParserOptionsSpecifies options for a UriParser.
Public enumerationLoaderOptimizationAn enumeration used to specify loader optimizations for an executable.
Public enumerationMidpointRoundingSpecifies how mathematical rounding methods should process a number that is midway between two numbers.
Public enumerationPlatformIDIdentifies the operating system, or development platform, supported by an assembly.
Public enumerationStringComparisonSpecifies the culture, case, and sort rules to be used by certain overloads of the String.Compare and String.Equals methods.
Public enumerationStringSplitOptionsSpecifies whether methods that split delimited substrings include or omit empty substrings from the returned array.
Public enumerationTypeCodeSpecifies the type of an object.
Public enumerationUriComponentsSpecifies the parts of a Uri.
Public enumerationUriFormatControls how URI information is escaped.
Public enumerationUriHostNameTypeDefines host name types for the Uri.CheckHostName method.
Public enumerationUriIdnScopeProvides the possible values for the configuration setting Internationalized Domain Name parsing.
Public enumerationUriKindDefines the kinds of Uris for several Uri.Uri methods.

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