Namespace: System.Runtime.InteropServices

The System.Runtime.InteropServices namespace provides a collection of classes useful for accessing COM objects, and native APIs from .NET. The types in this namespace fall into the following areas of functionality: attributes, exceptions, managed definitions of COM types, wrappers, type converters, and the Marshal class.

Many attributes are provided as a means of controlling marshaling behavior, such as how a structure should be arranged, or how a String should be represented. Of the most important attributes are , which is used to define methods that access native system APIs, and , which indicates how data should be marshaled between managed and unmanaged memory. Some attributes have corresponding enumerations that specify valid values for the attribute. They are listed below their associated attribute and are prefixed with the "-" character. The attributes provided by are:

AutomationProxyAttribute

ClassInterfaceAttribute

-ClassInterfaceType

ComAliasNameAttribute

ComConvertionLossAttribute

ComImportAttribute

ComRegisterFunctionAttribute

ComSourceInterfacesAttribute

ComUnregisterFunctionAttribute

ComVisibleAttribute

DispIdAttribute

DllImportAttribute

-CallingConvention

-CharSet

FieldOffsetAttribute

GuidAttribute

IDispatchImplAttribute

-IDispatchImplType

ImportedFromTypeLibAttribute

InAttribute

InterfaceTypeAttribute

-ComInterfaceType

LCIDConvertionAttribute

MarshalAsAttribute

-VarEnum

-UnmanagedType

OptionalAttribute

OutAttribute

PreserveSigAttribute

PrimaryInteropAssemblyAttribute

ProdIdAttribute

StructLayoutAttribute

-CharSet

-LayoutKind

TypeLibFuncAttribute

-TypeLibFuncFlags

TypeLibTypeAttribute

-TypeLibTypeFlags

TypeLibVarAttribute

-TypeLibVarFlags

The exception classes provided by indicate exceptional circumstances such as errors while performing certain operations, and serve as a way to bridge COM HRESULTs to .NET exceptions. The exceptions provided by are:

COMException

ExternalException

InvalidComObjectException

InvalidOleVariantTypeException

MarshalDirectiveException

SafeArrayRankMismatchException

SafeArrayTypeMismatchException

SEHException

It is occasionally necessary to use existing COM types from managed code. To do so, a managed definition of the COM type must be available for the managed user to bind to. The namespace provides managed definitions of a handful of useful interfaces. For detailed information on the types, refer to the existing documentation in the MSDN library. The COM types provided by are:

BINDPTR

BIND_OPTS

CALLCONV

CONNECTDATA

DESCKIND

DISPPARAMS

ELEMDESC

ELEMDESC.DESCUNION

EXCEPINFO

FILETIME

FUNCDESC

FUNCFLAGS

FUNCKIND

IDLDESC

IDLFLAG

IMPLTYPEFLAGS

INVOKEKIND

LIBFLAGS

PARAMDESC

PARAMFLAG

STATSTG

SYSKIND

TYPEATTR

TYPEDESC

TYPEFLAGS

TYPEKIND

TYPELIBATTR

UCOMIBindCtx

UCOMIConnectionPoint

UCOMIConnectionPointContainer

UCOMIEnumConnectionPoints

UCOMIEnumConnections

UCOMIEnumMoniker

UCOMIEnumStream

UCOMIEnumVARIANT

UCOMIMoniker

UCOMIPersistFile

UCOMIRunningObjectTable

UCOMIStream

VARDESC

VARDESC.DESCUNION

VARFLAGS

When using COM Variants, it is sometimes necessary to wrap a COM type in a managed class in order to control the type of the Variant. Several wrappers have been designed to deal with these situations. The wrapper classes provided by are:

CurrencyWrapper

DispatchWrapper

ErrorWrapper

UnknownWrapper

Although tools are provided in the .NET Framework SDK for registering types and converting between type libraries and assemblies, it is also possible to do the same conversion and registration tasks with the classes and interfaces found in the I namespace. The conversion and registration classes provided by are:

AssemblyRegistrationFlags

ExporterEventKind

ImporterEventKind

IRegistrationServices

ITypeLibConverter

ITypeLibExporterNotifySink

ITypeLibImporterNotifySink

RegistrationServices

TypeLibConverter

TypeLibExporterFlags

TypeLibImporterFlags

The class is the largest class in, and most important part of, . It is used primarily for unmanaged memory operations and building custom marshalers, a bridge between managed and unmanaged code.

Members of System.Runtime.InteropServices Namespace

Classes

Class	Description
class COMException	The exception thrown when an unrecognized HRESULT is returned from a COM method call.
class DllImportAttribute	Indicates that the attributed method is implemented as an export from an unmanaged DLL.
class ExternalException	The base exception type for all COM interop exceptions and structured exception handling (SEH) exceptions.
class FieldOffsetAttribute	Indicates the physical position of fields within the unmanaged representation of a class or structure.
class InAttribute	Indicates that data should be marshaled from the caller to the callee.
class InvalidOleVariantTypeException	The exception thrown by the marshaler when it encounters an argument of a variant type that can not be marshaled to managed code.
class Marshal	Provides a collection of methods pertaining to allocating unmanaged memory, copying unmanaged memory blocks, and converting managed to unmanaged types.
class MarshalAsAttribute	Indicates how the data should be marshaled between managed and unmanaged code.
class MarshalDirectiveException	The exception that is thrown by the marshaler when it encounters a MarshalAsAttribute it does not support.
class OptionalAttribute	Indicates that a parameter is optional.
class OutAttribute	Indicates that data should be marshaled from callee back to caller.
class PreserveSigAttribute	Indicates that the HRESULT or retval signature transformation that takes place during COM interop calls should be suppressed.
class RuntimeEnvironment	Provides a collection of methods that return information about the common language runtime environment.
class SEHException	Represents Structured Exception Handler (SEH) errors.
class StructLayoutAttribute	The class allows the user to control the physical layout of the data fields of a class or structure.

Interfaces

Interface	Description
interface ICustomMarshaler	Designed to provide custom wrappers for handling method calls.

Structures

Structure	Description
structure ArrayWithOffset	Encapsulates an array and an offset within the specified array.
structure GCHandle	Provides a means for accessing a managed object from unmanaged memory.
structure HandleRef	Wraps a managed object holding a handle to a resource that is passed to unmanaged code using platform invoke.

Enumerations

Enumeration	Description
enumeration CallingConvention	Specifies the calling convention required to call methods implemented in unmanaged code.
enumeration CharSet	Dictates which character set marshaled strings should use.
enumeration GCHandleType	Represents the types of handles the GCHandle class can allocate.
enumeration LayoutKind	Controls the layout of an object when exported to unmanaged code.
enumeration UnmanagedType	Identifies how parameters or fields should be marshaled to unmanaged code.
enumeration VarEnum	Indicates how the array elements should be marshaled when an array is marshaled from managed to unmanaged code as a System.Runtime.InteropServices.UnmanagedType.SafeArray (not supported on the shared source CLI) .