System Namespace

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

Classes

  Class Description
Public class AppDomain Represents an application domain, which is an isolated environment where applications execute. This class cannot be inherited.
Public class AppDomainUnloadedException The exception that is thrown when an attempt is made to access an unloaded application domain.
Public class ApplicationException The exception that is thrown when a non-fatal application error occurs.
Public class ArgumentException The exception that is thrown when one of the arguments provided to a method is not valid.
Public class ArgumentNullException The 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 class 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.
Public class Array Provides methods for creating, manipulating, searching, and sorting arrays, thereby serving as the base class for all arrays in the common language runtime.
Public class Attribute Represents the base class for custom attributes.
Public class AttributeUsageAttribute Specifies the usage of another attribute class. This class cannot be inherited.
Public class CLSCompliantAttribute Indicates whether a program element is compliant with the Common Language Specification (CLS). This class cannot be inherited.
Public class Convert Converts to and from base64-encoded strings.
Public class DBNull Represents a nonexistent value. This class cannot be inherited.
Public class 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.
Public class Enum Provides the base class for enumerations.
Public class Environment Provides information about, and means to manipulate, the current environment and platform. This class cannot be inherited.
Public class Exception Represents errors that occur during application execution.
Public class FlagsAttribute Indicates that an enumeration can be treated as a bit field; that is, a set of flags.
Public class GC Controls the system garbage collector, a service that automatically reclaims unused memory.
Public class 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.
Public class InvalidCastException The exception that is thrown for invalid casting or explicit conversion.
Public class InvalidOperationException The exception that is thrown when a method call is invalid for the object's current state.
Public class MarshalByRefObject Enables access to objects across application domain boundaries in applications that support remoting.
Public class Math Provides constants and static methods for trigonometric, logarithmic, and other common mathematical functions.
Public class MTAThreadAttribute Indicates that the COM threading model for an application is multithreaded apartment (MTA).
Public class MulticastDelegate Represents a multicast delegate; that is, a delegate that can have more than one element in its invocation list.
Public class NonSerializedAttribute Indicates that a field of a serializable class should not be serialized. This class cannot be inherited.
Public class NotImplementedException The exception that is thrown when a requested method or operation is not implemented.
Public class 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.
Public class NullReferenceException The exception that is thrown when there is an attempt to dereference a null object reference.
Public class 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.
Public class ObjectDisposedException The exception that is thrown when an operation is performed on a disposed object.
Public class ObsoleteAttribute Marks the program elements that are no longer in use. This class cannot be inherited.
Public class OutOfMemoryException The exception that is thrown when there is not enough memory to continue the execution of a program.
Public class ParamArrayAttribute Indicates that a method will allow a variable number of arguments in its invocation. This class cannot be inherited.
Public class Random Represents a pseudo-random number generator, a device that produces a sequence of numbers that meet certain statistical requirements for randomness.
Public class SerializableAttribute Indicates that a class can be serialized. This class cannot be inherited.
Public class STAThreadAttribute Indicates that the COM threading model for an application is single-threaded apartment (STA).
Public class String Represents text as a series of Unicode characters.
Public class SystemException Defines the base class for predefined exceptions in the System namespace.
Public class TimeZone Represents a time zone.
Public class 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.
Public class Uri Provides an object representation of a uniform resource identifier (URI) and easy access to the parts of the URI.
Public class ValueType Provides the base class for value types.
Public class Version Represents the version number of an assembly, operating system, or the common language runtime. This class cannot be inherited.
Public class WeakReference Represents a weak reference, which references an object while still allowing that object to be reclaimed by garbage collection.

Structures

  Structure Description
Public structure Boolean Represents a Boolean value.
Public structure Byte Represents an 8-bit unsigned integer.
Public structure Char Represents a character as a UTF-16 code unit.
Public structure DateTime Represents an instant in time, typically expressed as a date and time of day.
Public structure Decimal Represents a decimal number.
Public structure Double Represents a double-precision floating-point number.
Public structure Guid Represents a globally unique identifier (GUID).
Public structure Int16 Represents a 16-bit signed integer.
Public structure Int32 Represents a 32-bit signed integer.
Public structure Int64 Represents a 64-bit signed integer.
Public structure IntPtr A platform-specific type that is used to represent a pointer or a handle.
Public structure RuntimeArgumentHandle References a variable-length argument list.
Public structure RuntimeFieldHandle Represents a field using an internal metadata token.
Public structure RuntimeMethodHandle RuntimeMethodHandle is a handle to the internal metadata representation of a method.
Public structure RuntimeTypeHandle Represents a type using an internal metadata token.
Public structure SByte Represents an 8-bit signed integer.
Public structure Single Represents a single-precision floating-point number.
Public structure TimeSpan Represents a time interval.
Public structure TypedReference Describes 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 structure UInt16 Represents a 16-bit unsigned integer.
Public structure UInt32 Represents a 32-bit unsigned integer.
Public structure UInt64 Represents a 64-bit unsigned integer.
Public structure UIntPtr A platform-specific type that is used to represent a pointer or a handle.
Public structure Void Specifies a return value type for a method that does not return a value.

Interfaces

  Interface Description
Public interface IAsyncResult Represents the status of an asynchronous operation.
Public interface ICloneable Supports cloning, which creates a new instance of a class with the same value as an existing instance.
Public interface IComparable Defines a generalized type-specific comparison method that a value type or class implements to order or sort its instances.
Public interface ICustomFormatter Defines a method that supports custom formatting of the value of an object.
Public interface IDisposable Defines a method to release allocated resources.
Public interface IFormatProvider Provides a mechanism for retrieving an object to control formatting.
Public interface IFormattable Provides functionality to format the value of an object into a string representation.

Delegates

  Delegate Description
Public delegate AsyncCallback References a method to be called when a corresponding asynchronous operation completes.

Enumerations

  Enumeration Description
Public enumeration AttributeTargets Specifies the application elements on which it is valid to apply an attribute.
Public enumeration 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.
Public enumeration DayOfWeek Specifies the day of the week.
Public enumeration TypeCode Specifies the type of an object.
Protected enumeration Uri. . :: . .Flags Defines flags for URI.
Public enumeration UriHostNameType Defines host name types for the Uri.CheckHostName method.
Public enumeration UriKind Defines the kinds of Uris for the Uri..::..IsWellFormedUriString(String, UriKind) and several Uri..::..Uri methods.