Members of this namespace provide several categories of functionality, as shown in the following table. Attributes control marshaling behavior, such as how to arrange structures or how to represent strings. The most important attributes are DllImportAttribute, which you use to define platform invoke methods for accessing unmanaged APIs, and MarshalAsAttribute, which you use to specify how data is marshaled between managed and unmanaged memory.

 Classes

	Class	Description
	AllowReversePInvokeCallsAttribute	Allows an unmanaged method to call a managed method.
	AutomationProxyAttribute	Specifies whether the type should be marshaled using the Automation marshaler or a custom proxy and stub.
	BestFitMappingAttribute	Controls whether Unicode characters are converted to the closest matching ANSI characters.
	BStrWrapper	Marshals data of type VT_BSTR from managed to unmanaged code. This class cannot be inherited.
	ClassInterfaceAttribute	Indicates the type of class interface to be generated for a class exposed to COM, if an interface is generated at all.
	CoClassAttribute	Specifies the class identifier of a coclass imported from a type library.
	ComAliasNameAttribute	Indicates the COM alias for a parameter or field type.
	ComCompatibleVersionAttribute	Indicates to a COM client that all classes in the current version of an assembly are compatible with classes in an earlier version of the assembly.
	ComConversionLossAttribute	Indicates that information was lost about a class or interface when it was imported from a type library to an assembly.
	ComDefaultInterfaceAttribute	Specifies a default interface to expose to COM. This class cannot be inherited.
	ComEventInterfaceAttribute	Identifies the source interface and the class that implements the methods of the event interface that is generated when a coclass is imported from a COM type library.
	COMException	The exception that is thrown when an unrecognized HRESULT is returned from a COM method call.
	ComImportAttribute	Indicates that the attributed type was previously defined in COM.
	ComRegisterFunctionAttribute	Specifies the method to call when you register an assembly for use from COM; this enables the execution of user-written code during the registration process.
	ComSourceInterfacesAttribute	Identifies a list of interfaces that are exposed as COM event sources for the attributed class.
	ComUnregisterFunctionAttribute	Specifies the method to call when you unregister an assembly for use from COM; this allows for the execution of user-written code during the unregistration process.
	ComVisibleAttribute	Controls accessibility of an individual managed type or member, or of all types within an assembly, to COM.
	CriticalHandle	Represents a wrapper class for handle resources.
	CurrencyWrapper	Wraps objects the marshaler should marshal as a VT_CY.
	DefaultCharSetAttribute	Specifies the value of the CharSet enumeration. This class cannot be inherited.
	DefaultParameterValueAttribute	Sets the default value of a parameter when called from a language that supports default parameters. This class cannot be inherited.
	DispatchWrapper	Wraps objects the marshaler should marshal as a VT_DISPATCH.
	DispIdAttribute	Specifies the COM dispatch identifier (DISPID) of a method, field, or property.
	DllImportAttribute	Indicates that the attributed method is exposed by an unmanaged dynamic-link library (DLL) as a static entry point.
	ErrorWrapper	Wraps objects the marshaler should marshal as a VT_ERROR.
	ExtensibleClassFactory	Enables customization of managed objects that extend from unmanaged objects during creation.
	ExternalException	The base exception type for all COM interop exceptions and structured exception handling (SEH) exceptions.
	FieldOffsetAttribute	Indicates the physical position of fields within the managed and unmanaged representation of a class or structure.
	GuidAttribute	Supplies an explicit System..::.Guid when an automatic GUID is undesirable.
	HandleCollector	Tracks outstanding handles and forces a garbage collection when the specified threshold is reached.
	IDispatchImplAttribute	Obsolete. Indicates which IDispatch implementation the common language runtime uses when exposing dual interfaces and dispinterfaces to COM.
	ImportedFromTypeLibAttribute	Indicates that the types defined within an assembly were originally defined in a type library.
	InAttribute	Indicates that data should be marshaled from the caller to the callee, but not back to the caller.
	InterfaceTypeAttribute	Indicates whether a managed interface is dual, dispatch-only, or IUnknown -only when exposed to COM.
	InvalidComObjectException	The exception thrown when an invalid COM object is used.
	InvalidOleVariantTypeException	The exception thrown by the marshaler when it encounters an argument of a variant type that can not be marshaled to managed code.
	LCIDConversionAttribute	Indicates that a method's unmanaged signature expects a locale identifier (LCID) parameter.
	Marshal	Provides a collection of methods for allocating unmanaged memory, copying unmanaged memory blocks, and converting managed to unmanaged types, as well as other miscellaneous methods used when interacting with unmanaged code.
	MarshalAsAttribute	Indicates how to marshal the data between managed and unmanaged code.
	MarshalDirectiveException	The exception that is thrown by the marshaler when it encounters a MarshalAsAttribute it does not support.
	OptionalAttribute	Indicates that a parameter is optional.
	OutAttribute	Indicates that data should be marshaled from callee back to caller.
	PreserveSigAttribute	Indicates that the HRESULT or retval signature transformation that takes place during COM interop calls should be suppressed.
	PrimaryInteropAssemblyAttribute	Indicates that the attributed assembly is a primary interop assembly.
	ProgIdAttribute	Allows the user to specify the ProgID of a class.
	RegistrationServices	Provides a set of services for registering and unregistering managed assemblies for use from COM.
	RuntimeEnvironment	Provides a collection of static methods that return information about the common language runtime environment.
	SafeArrayRankMismatchException	The exception thrown when the rank of an incoming SAFEARRAY does not match the rank specified in the managed signature.
	SafeArrayTypeMismatchException	The exception thrown when the type of the incoming SAFEARRAY does not match the type specified in the managed signature.
	SafeHandle	Represents a wrapper class for operating system handles. This class must be inherited.
	SEHException	Represents Structured Exception Handler (SEH) errors.
	SetWin32ContextInIDispatchAttribute	Obsolete. This attribute has been deprecated.
	StandardOleMarshalObject	Replaces the standard common language runtime (CLR) free-threaded marshaler with the standard OLE STA marshaler.
	StructLayoutAttribute	The StructLayoutAttribute class allows the user to control the physical layout of the data fields of a class or structure.
	TypeLibConverter	Provides a set of services that convert a managed assembly to a COM type library and vice versa.
	TypeLibFuncAttribute	Contains the FUNCFLAGS that were originally imported for this method from the COM type library.
	TypeLibImportClassAttribute	Specifies which Type exclusively uses an interface. This class cannot be inherited.
	TypeLibTypeAttribute	Contains the TYPEFLAGS that were originally imported for this type from the COM type library.
	TypeLibVarAttribute	Contains the VARFLAGS that were originally imported for this field from the COM type library.
	TypeLibVersionAttribute	Specifies the version number of an exported type library.
	UnknownWrapper	Wraps objects the marshaler should marshal as a VT_UNKNOWN.
	UnmanagedFunctionPointerAttribute	Controls the marshaling behavior of a delegate signature passed as an unmanaged function pointer to or from unmanaged code. This class cannot be inherited.
	VariantWrapper	Marshals data of type VT_VARIANT | VT_BYREF from managed to unmanaged code. This class cannot be inherited.

 Structures

	Structure	Description
	ArrayWithOffset	Encapsulates an array and an offset within the specified array.
	BIND_OPTS	Obsolete. Use System.Runtime.InteropServices.ComTypes..::.BIND_OPTS instead.
	BINDPTR	Obsolete. Use System.Runtime.InteropServices.ComTypes..::.BINDPTR instead.
	CONNECTDATA	Obsolete. Use System.Runtime.InteropServices.ComTypes..::.CONNECTDATA instead.
	DISPPARAMS	Obsolete. Use System.Runtime.InteropServices.ComTypes..::.DISPPARAMS instead.
	ELEMDESC	Obsolete. Use System.Runtime.InteropServices.ComTypes..::.ELEMDESC instead.
	ELEMDESC..::.DESCUNION	Use System.Runtime.InteropServices.ComTypes..::.ELEMDESC..::.DESCUNION instead.
	EXCEPINFO	Obsolete. Use System.Runtime.InteropServices.ComTypes..::.EXCEPINFO instead.
	FILETIME	Obsolete. Use System.Runtime.InteropServices.ComTypes..::.FILETIME instead.
	FUNCDESC	Obsolete. Use System.Runtime.InteropServices.ComTypes..::.FUNCDESC instead.
	GCHandle	Provides a means for accessing a managed object from unmanaged memory.
	HandleRef	Wraps a managed object holding a handle to a resource that is passed to unmanaged code using platform invoke.
	IDLDESC	Obsolete. Use System.Runtime.InteropServices.ComTypes..::.IDLDESC instead.
	PARAMDESC	Obsolete. Use System.Runtime.InteropServices.ComTypes..::.PARAMDESC instead.
	STATSTG	Obsolete. Use System.Runtime.InteropServices.ComTypes..::.STATSTG instead.
	TYPEATTR	Obsolete. Use System.Runtime.InteropServices.ComTypes..::.TYPEATTR instead.
	TYPEDESC	Obsolete. Use System.Runtime.InteropServices.ComTypes..::.TYPEDESC instead.
	TYPELIBATTR	Obsolete. Use System.Runtime.InteropServices.ComTypes..::.TYPELIBATTR instead.
	VARDESC	Obsolete. Use System.Runtime.InteropServices.ComTypes..::.VARDESC instead.
	VARDESC..::.DESCUNION	Use System.Runtime.InteropServices.ComTypes..::.VARDESC..::.DESCUNION instead.

 Interfaces

	Interface	Description
	_Activator	Exposes the System..::.Activator class to unmanaged code.
	_Assembly	Exposes the public members of the System.Reflection..::.Assembly class to unmanaged code.
	_AssemblyBuilder	Exposes the System.Reflection.Emit..::.AssemblyBuilder class to unmanaged code.
	_AssemblyName	Exposes the AssemblyName class to unmanaged code.
	_Attribute	Exposes the System..::.Attribute class to unmanaged code.
	_ConstructorBuilder	Exposes the System.Reflection.Emit..::.ConstructorBuilder class to unmanaged code.
	_ConstructorInfo	Exposes the public members of the System.Reflection..::.ConstructorInfo class to unmanaged code.
	_CustomAttributeBuilder	Exposes the System.Reflection.Emit..::.CustomAttributeBuilder class to unmanaged code.
	_EnumBuilder	Exposes the System.Reflection.Emit..::.EnumBuilder class to unmanaged code.
	_EventBuilder	Exposes the System.Reflection.Emit..::.EventBuilder class to unmanaged code.
	_EventInfo	Exposes the public members of the System.Reflection..::.EventInfo class to unmanaged code.
	_Exception	Exposes the public members of the System..::.Exception class to unmanaged code.
	_FieldBuilder	Exposes the System.Reflection.Emit..::.FieldBuilder class to unmanaged code.
	_FieldInfo	Exposes the public members of the System.Reflection..::.FieldInfo class to unmanaged code.
	_ILGenerator	Exposes the System.Reflection.Emit..::.ILGenerator class to unmanaged code.
	_LocalBuilder	Exposes the System.Reflection.Emit..::.LocalBuilder class to unmanaged code.
	_MemberInfo	Exposes the public members of the System.Reflection..::.MemberInfo class to unmanaged code.
	_MethodBase	Exposes the public members of the System.Reflection..::.MethodBase class to unmanaged code.
	_MethodBuilder	Exposes the MethodBuilder class to unmanaged code.
	_MethodInfo	Exposes the public members of the System.Reflection..::.MethodInfo class to unmanaged code.
	_MethodRental	Exposes the System.Reflection.Emit..::.MethodRental class to unmanaged code.
	_Module	Exposes the Module class to unmanaged code.
	_ModuleBuilder	Exposes the System.Reflection.Emit..::.ModuleBuilder class to unmanaged code.
	_ParameterBuilder	Exposes the System.Reflection.Emit..::.ParameterBuilder class to unmanaged code.
	_ParameterInfo	Exposes the System.Reflection..::.ParameterInfo class to unmanaged code.
	_PropertyBuilder	Exposes the System.Reflection.Emit..::.PropertyBuilder class to unmanaged code.
	_PropertyInfo	Exposes the public members of the System.Reflection..::.PropertyInfo class to unmanaged code.
	_SignatureHelper	Exposes the System.Reflection.Emit..::.SignatureHelper class to unmanaged code.
	_Thread	Exposes the System.Threading..::.Thread class to unmanaged code.
	_Type	Exposes the public members of the System..::.Type class to the unmanaged code.
	_TypeBuilder	Exposes the System.Reflection.Emit..::.TypeBuilder class to unmanaged code.
	ICustomAdapter	Provides a way for clients to access the actual object, rather than the adapter object handed out by a custom marshaler.
	ICustomFactory	Enables users to write activation code for managed objects that extend MarshalByRefObject.
	ICustomMarshaler	Designed to provide custom wrappers for handling method calls.
	IRegistrationServices	Provides a set of services for registering and unregistering managed assemblies for use from COM.
	ITypeLibConverter	Provides a set of services that convert a managed assembly to a COM type library and vice versa.
	ITypeLibExporterNameProvider	Provides control over the casing of names when exported to a type library.
	ITypeLibExporterNotifySink	Provides a callback mechanism for the assembly converter to inform the caller of the status of the conversion, and involve the caller in the conversion process itself.
	ITypeLibImporterNotifySink	Provides a callback mechanism for the type library converter to inform the caller of the status of the conversion, and involve the caller in the conversion process itself.
	UCOMIBindCtx	Obsolete. Use System.Runtime.InteropServices.ComTypes..::.BIND_OPTS instead.
	UCOMIConnectionPoint	Obsolete. Use System.Runtime.InteropServices.ComTypes..::.IConnectionPoint instead.
	UCOMIConnectionPointContainer	Obsolete. Use System.Runtime.InteropServices.ComTypes..::.IConnectionPointContainer instead.
	UCOMIEnumConnectionPoints	Obsolete. Use System.Runtime.InteropServices.ComTypes..::.IEnumConnectionPoints instead.
	UCOMIEnumConnections	Obsolete. Use System.Runtime.InteropServices.ComTypes..::.IEnumConnections instead.
	UCOMIEnumMoniker	Obsolete. Use System.Runtime.InteropServices.ComTypes..::.IEnumMoniker instead.
	UCOMIEnumString	Obsolete. Use System.Runtime.InteropServices.ComTypes..::.IEnumString instead.
	UCOMIEnumVARIANT	Obsolete. Use System.Runtime.InteropServices.ComTypes..::.IEnumVARIANT instead.
	UCOMIMoniker	Obsolete. Use System.Runtime.InteropServices.ComTypes..::.IMoniker instead.
	UCOMIPersistFile	Obsolete. Use System.Runtime.InteropServices.ComTypes..::.IPersistFile instead.
	UCOMIRunningObjectTable	Obsolete. Use System.Runtime.InteropServices.ComTypes..::.IRunningObjectTable instead.
	UCOMIStream	Obsolete. Use System.Runtime.InteropServices.ComTypes..::.IStream instead.
	UCOMITypeComp	Obsolete. Use System.Runtime.InteropServices.ComTypes..::.ITypeComp instead.
	UCOMITypeInfo	Obsolete. Use System.Runtime.InteropServices.ComTypes..::.ITypeInfo instead.
	UCOMITypeLib	Obsolete. Use System.Runtime.InteropServices.ComTypes..::.ITypeLib instead.

 Delegates

	Delegate	Description
	ObjectCreationDelegate	Creates a COM object.

 Enumerations

	Enumeration	Description
	AssemblyRegistrationFlags	Defines a set of flags used when registering assemblies.
	CALLCONV	Obsolete. Use System.Runtime.InteropServices.ComTypes..::.CALLCONV instead.
	CallingConvention	Specifies the calling convention required to call methods implemented in unmanaged code.
	CharSet	Dictates which character set marshaled strings should use.
	ClassInterfaceType	Identifies the type of class interface that is generated for a class.
	ComInterfaceType	Identifies how to expose an interface to COM.
	ComMemberType	Describes the type of a COM member.
	DESCKIND	Obsolete. Use System.Runtime.InteropServices.ComTypes..::.DESCKIND instead.
	ExporterEventKind	Describes the callbacks that the type library exporter makes when exporting a type library.
	FUNCFLAGS	Obsolete. Use System.Runtime.InteropServices.ComTypes..::.FUNCFLAGS instead.
	FUNCKIND	Obsolete. Use System.Runtime.InteropServices.ComTypes..::.FUNCKIND instead.
	GCHandleType	Represents the types of handles the GCHandle class can allocate.
	IDispatchImplType	Obsolete. Indicates which IDispatch implementation to use for a particular class.
	IDLFLAG	Obsolete. Use System.Runtime.InteropServices.ComTypes..::.IDLFLAG instead.
	IMPLTYPEFLAGS	Obsolete. Use System.Runtime.InteropServices.ComTypes..::.IMPLTYPEFLAGS instead.
	ImporterEventKind	Describes the callbacks that the type library importer makes when importing a type library.
	INVOKEKIND	Obsolete. Use System.Runtime.InteropServices.ComTypes..::.INVOKEKIND instead.
	LayoutKind	Controls the layout of an object when exported to unmanaged code.
	LIBFLAGS	Obsolete. Use System.Runtime.InteropServices.ComTypes..::.LIBFLAGS instead.
	PARAMFLAG	Obsolete. Use System.Runtime.InteropServices.ComTypes..::.PARAMFLAG instead.
	RegistrationClassContext	Specifies the set of execution contexts in which a class object will be made available for requests to construct instances.
	RegistrationConnectionType	Defines the types of connections to a class object.
	SYSKIND	Obsolete. Use System.Runtime.InteropServices.ComTypes..::.SYSKIND instead.
	TYPEFLAGS	Obsolete. Use System.Runtime.InteropServices.ComTypes..::.TYPEFLAGS instead.
	TYPEKIND	Obsolete. Use System.Runtime.InteropServices.ComTypes..::.TYPEKIND instead.
	TypeLibExporterFlags	Indicates how a type library should be produced.
	TypeLibFuncFlags	Describes the original settings of the FUNCFLAGS in the COM type library from where this method was imported.
	TypeLibImporterFlags	Indicates how an assembly should be produced.
	TypeLibTypeFlags	Describes the original settings of the TYPEFLAGS in the COM type library from which the type was imported.
	TypeLibVarFlags	Describes the original settings of the VARFLAGS in the COM type library from which the variable was imported.
	UnmanagedType	Identifies how to marshal parameters or fields to unmanaged code.
	VarEnum	Indicates how to marshal the array elements when an array is marshaled from managed to unmanaged code as a UnmanagedType..::.SafeArray.
	VARFLAGS	Obsolete. Use System.Runtime.InteropServices.ComTypes..::.VARFLAGS instead.