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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.

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 classActivationContextIdentifies the activation context for the current application. This class cannot be inherited.
Public classActivatorContains methods to create types of objects locally or remotely, or obtain references to existing remote objects. This class cannot be inherited.
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 classApplicationIdContains information used to uniquely identify an application. This class cannot be inherited.
Public classApplicationIdentityProvides the ability to uniquely identify a manifest-activated application. This class cannot be inherited.
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 classAssemblyLoadEventArgsProvides data for the AssemblyLoad event.
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 classCharEnumeratorSupports iterating over a String object and reading its individual characters. This class cannot be inherited.
Public classCLSCompliantAttributeIndicates whether a program element is compliant with the Common Language Specification (CLS). This class cannot be inherited.
Public classConsoleRepresents the standard input, output, and error streams for console applications. This class cannot be inherited.
Public classConsoleCancelEventArgsProvides data for the Console.CancelKeyPress event. This class cannot be inherited.
Public classContextBoundObjectDefines the base class for all context-bound classes.
Public classContextMarshalExceptionThe exception that is thrown when an attempt to marshal an object across a context boundary fails.
Public classContextStaticAttributeIndicates 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 null value.
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 classDuplicateWaitObjectExceptionThe exception that is thrown when an object appears more than once in an array of synchronization objects.
Public classEntryPointNotFoundExceptionThe exception that is thrown when an attempt to load a class fails due to the absence of an entry method.
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 classExecutionEngineExceptionThe 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 classGopherStyleUriParserA customizable parser based on the Gopher scheme.
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 classInsufficientMemoryExceptionThe exception that is thrown when a check for sufficient available memory fails. 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 classLdapStyleUriParserA customizable parser based on the Lightweight Directory Access Protocol (LDAP) scheme.
Public classLoaderOptimizationAttributeUsed to set the default loader optimization policy for the main method of an executable application.
Public classLocalDataStoreSlotEncapsulates a memory slot to store local data. This class cannot be inherited.
Public classMarshalByRefObjectEnables access to objects across application domain boundaries in applications that support remoting.
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 classNetPipeStyleUriParserA parser based on the NetPipe scheme for the "Indigo" system.
Public classNetTcpStyleUriParserA parser based on the NetTcp scheme for the "Indigo" system.
Public classNewsStyleUriParserA customizable parser based on the news scheme using the Network News Transfer Protocol (NNTP).
Public classNonSerializedAttributeIndicates that a field of a serializable class should not be serialized. 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 a null reference (Nothing in Visual Basic) 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 the 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 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 TypeResolve, ResourceResolve, and AssemblyResolve events.
Public classSerializableAttributeIndicates that a class can be serialized. This class cannot be inherited.
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 classTimeZoneRepresents a time zone.
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 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 classTypeUnloadedExceptionThe exception that is thrown when there is an attempt to access an unloaded class.
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 by the 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 a String type to a Uri type, and vice versa.
Public classValueTypeProvides the base class for value types.
Public classVersionRepresents the version number for a common language runtime assembly. This class cannot be inherited.
Public classWeakReferenceRepresents a weak reference, which references an object while still allowing that object to be garbage collected.
 InterfaceDescription
Public interface_AppDomainExposes the public members of the System.AppDomain class to unmanaged code.
Public interfaceIAppDomainSetupRepresents assembly binding information that can be added to an instance of AppDomain.
Public interfaceIAsyncResultRepresents the status of an asynchronous operation.
Public interfaceICloneableSupports cloning, which creates a new instance of a class with the same value as an existing instance.
Public interfaceIComparableDefines a generalized comparison method that a value type or class implements to create a type-specific comparison method.
Public interfaceIComparableDefines 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 unmanaged resources.
Public interfaceIEquatableDefines 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 interfaceIServiceProviderDefines a mechanism for retrieving a service object; that is, an object that provides custom support to other objects.
 StructureDescription
Public structureArgIteratorRepresents a variable-length argument list; that is, the parameters of a function that takes a variable number of arguments.
Public structureArraySegmentDelimits 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 structureConsoleKeyInfoDescribes the console key that was pressed, including the character represented by the console key and the state of the SHIFT, ALT, and CTRL modifier keys.
Public structureDateTimeRepresents an instant in time, typically expressed as a date and time of day.
Public structureDecimalRepresents a decimal number.
Public structureDoubleRepresents a double-precision floating-point number.
Public structureEnumProvides the base class for enumerations.
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 structureModuleHandleRepresents a runtime handle for a module.
Public structureNullableRepresents an object whose underlying type is a value type that can also be assigned a null reference (Nothing in Visual Basic) 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 structureTypedReferenceDescribes objects that contain both a managed pointer to a location and a runtime representation of the type that may be stored at that location.
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.
 DelegateDescription
Public delegateActionRepresents the method that performs an action on the specified object.
Public delegateAppDomainInitializerRepresents the callback method to invoke when the application domain is initialized.
Public delegateAssemblyLoadEventHandlerRepresents the method that handles the AssemblyLoad event of an AppDomain.
Public delegateAsyncCallbackReferences the callback method to be called when the asynchronous operation is completed.
Public delegateComparisonRepresents the method that compares two objects of the same type.
Public delegateConsoleCancelEventHandlerRepresents the method that will handle the CancelKeyPress event of a System.Console.
Public delegateConverterRepresents a method that converts an object from one type to another type.
Public delegateCrossAppDomainDelegateUsed by DoCallBack for cross-application domain calls.
Public delegateEventHandlerRepresents the method that will handle an event that has no event data.
Public delegateEventHandlerRepresents the method that will handle an event. The generic type argument specifies the type of the event data generated by the event.
Public delegatePredicateRepresents the method that defines a set of criteria and determines whether the specified object meets those criteria.
Public delegateResolveEventHandlerRepresents the method that handles the TypeResolve, ResourceResolve, and AssemblyResolve events of an AppDomain.
Public delegateUnhandledExceptionEventHandlerRepresents the method that will handle the event raised by an exception that is not handled by the application domain.
 EnumerationDescription
Public enumerationActivationContext.ContextFormIndicates the context for a manifest-activated application.
Public enumerationAppDomainManagerInitializationOptionsSpecifies the action that a custom application domain manager takes when initializing a new domain.
Public enumerationAttributeTargetsSpecifies the application elements on which it is valid to apply an attribute.
Public enumerationBase64FormattingOptionsSpecifies whether relevant System.Convert.ToBase64CharArray and System.Convert.ToBase64String methods insert line breaks in their output.
Public enumerationConsoleColorSpecifies constants that define foreground and background colors for the console.
Public enumerationConsoleKeySpecifies the standard keys on a console.
Public enumerationConsoleModifiersRepresents the SHIFT, ALT, and CTRL modifier keys on a keyboard.
Public enumerationConsoleSpecialKeySpecifies combinations of modifier and console keys that can interrupt the current process.
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 enumerationEnvironmentVariableTargetSpecifies the location where an environment variable is stored or retrieved in a set or get operation.
Public enumerationGenericUriParserOptionsSpecifies options for a UriParser.
Public enumerationLoaderOptimizationAn enumeration used with the LoaderOptimizationAttribute class 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 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 applicable System.String.Split method overloads include or omit empty substrings from the return value.
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 enumerationUriKindDefines the kinds of Uris for the Uri.IsWellFormedUriString and several System.Uri methods.
Public enumerationUriPartialDefines the parts of a URI for the Uri.GetLeftPart method.
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