[From msdn] how to map hresult and exception

The com method reports an error by returning hresult; the. NET method reports an error by raising an exception. The runtime will process the conversion between the two .. . NET Framework maps each exception class to an hresult.

User-defined exception classes can specify any appropriate hresult. WhenHresultWhen fields are used to generate exceptions, these exception classes can dynamically change the returned hresult. Other information about the exception is passedIerrorinfoThe interface is provided to the client, which is implemented on. NET objects in an unmanaged process.

If an extension is createdSystem. ExceptionYou must set the hresult field during the construction process. Otherwise, the base class will assign the hresult value. By providing the hresult value in the exception constructor, You can map the new exception class to the existing hresult.

Note that when a thread existsIerrorinfoThe Runtime Library sometimes ignoresHresult. This behavior may occur inHresultAndIerrorinfoIt does not indicate the same error. 

Create an exception class and map it to hresult

• Use the followingCodeCreateNoaccessexceptionAnd map it to hresultE_accessdenied.

Class noaccessexception: Public Applicationexception
{
Noaccessexception (){
Hresult=E_accessdenied;
}
}
Cmyclass: methodthatthrows
{
Throw NewNoaccessexception ();
}

You may have encounteredProgram(Take anyProgramming LanguageWrite ). For example, in the following code example, use the custom SeparatorMarshal. throwexceptionforhr (INT hresult)Method to cause an exception with a specific hresult value. This method searches for this hresult and generates the corresponding exception type. For example, the hresult in the following code snippet will generateArgumentexception.

Cmyclass: methodthatthrows
{
Marshal. throwexceptionforhr (cor_e_argument );
}

The following table provides a complete link ing between each hresult and its comparable exception classes in. NET Framework.

Hresult	. Net exception
Msee_e_appdomainunloaded	Appdomainunloadedexception
Cor_e_application	Applicationexception
Cor_e_argument or e_invalidarg	Argumentexception
Cor_e_argumentoutofrange	Argumentoutofrangeexception
Cor_e_arithmetic or error_arithmetic_overflow	Arithmeticexception
Cor_e_arraytypemismatch	Arraytypemismatchexception
Cor_e_badimageformat or error_bad_format	Badimageformatexception
Cor_e_comemulate_error	Comemulateexception
Cor_e_contextmarshal	Contextexternalexception
Cor_e_core	Coreexception
Nte_fail	Cryptographicexception
Cor_e_directorynotfound or error_path_not_found	Directorynotfoundexception
Cor_e_dividebyzero	Dividebyzeroexception
Cor_e_duplicatewaitobject	Duplicatewaitobjectexception
Cor_e_endofstream	Endofstreamexception
Cor_e_typeload	Entrypointnotfoundexception
Cor_e_exception	Exception
Cor_e_executionengine	Executionengineexception
Cor_e_fieldaccess	Fieldaccessexception
Cor_e_filenotfound or error_file_not_found	Filenotfoundexception
Cor_e_format	Formatexception
Cor_e_indexoutofrange	Indexoutofrangeexception
Cor_e_invalidcast or e_nointerface	Invalidcastexception
Cor_e_invalidcomobject	Invalidcomobjectexception
Cor_e_invalidfiltercriteria	Invalidfiltercriteriaexception
Cor_e_invalidolevarianttype	Invalidolevarianttypeexception
Cor_e_invalidoperation	Invalidoperationexception
Cor_e_io	Ioexception
Cor_e_memberaccess	Accessexception
Cor_e_methodaccess	Methodaccessexception
Cor_e_missingfield	Missingfieldexception
Cor_e_missingmanifestresource	Missingmanifestresourceexception
Cor_e_missingmember	Missingmemberexception
Cor_e_missingmethod	Missingmethodexception
Cor_e_multicastnotsupported	Multicastnotsupportedexception
Cor_e_notfinitenumber	Notfinitenumberexception
E_notimpl	Notimplementedexception
Cor_e_notsupported	Notsupportedexception
Cor_e_nullreference or e_pointer	Nullreferenceexception
Cor_e_outofmemory or E_outofmemory	Outofmemoryexception
Cor_e_overflow	Overflowexception
Cor_e_pathtoolong or error_filename_exced_range	Pathtoolongexception
Cor_e_rank	Rankexception
Cor_e_reflectiontypeload	Reflectiontypeloadexception
Cor_e_remoting	Remotingexception
Cor_e_safearraytypemismatch	Safearraytypemismatchexception
Cor_e_security	Securityexception
Cor_e_serialization	Serializationexception
Cor_e_stackoverflow or error_stack_overflow	Stackoverflowexception
Cor_e_synchronizationlock	Synchronizationlockexception
Cor_e_system	Systemexception
Cor_e_target	Targetexception
Cor_e_targetinvocation	Targetinvocationexception
Cor_e_targetparamcount	Targetparametercountexception
Cor_e_threadaborted	Threadabortexception
Cor_e_threadinterrupted	Threadinterruptedexception
Cor_e_threadstate	Threadstateexception
Cor_e_threadstop	Threadstopexception
Cor_e_typeload	Typeloadexception
Cor_e_typeinitialization	Typeinitializationexception
Cor_e_verification	Verificationexception
Cor_e_weakreference	Weakreferenceexception
Cor_e_vtablecallsnotsupported	Vtablecallsnotsupportedexception
All other hresults	Comexception

To retrieve extended error information, the hosting client must check the fields of the generated exception object. To make the exception object provide useful information about the error, the COM object must be implementedIerrorinfoInterface. Running database usageIerrorinfoProvided information to initialize the exception object.

If the COM object is not supportedIerrorinfo, The Runtime Library will use the default value to initialize the exception object. The following table lists the fields associated with the exception object.IerrorinfoDefault information source.

Note: When ierrorinfo exists on the thread, the runtime database sometimes ignores hresult . This behavior may occur when hresult and ierrorinfo do not indicate the same error.

The string returned by The string returned by

exception field	com Information Source
errorcode	call the returned hresult.
helplink	If ierrorinfo-> helpcontext is not zero, strings are formed by concatenating ierrorinfo-> gethelpfile , "#", and ierrorinfo-> gethelpcontext . Otherwise, the string is returned from ierrorinfo-> gethelpfile .
innerexception	always blank reference ( nothing in Visual Basic ).
message	ierrorinfo-> getdescription .
source	ierrorinfo-> getsource .
stacktrace	stack trace.
targetsite	name of the method that returns the failed hresult.

Message,SourceAndStacktraceAnd other exception fields cannot be usedStackoverflowexception.