[CONNECT C++] Calling undocumented function dgnFileObj_getHighestElementID

Question

Hi, 
 in the Connect edition: is there any way, how to call undocumented function like: 
 unsigned __int64 Bentley::dgnFileObj_getHighestElementID(struct Bentley::DgnPlatform::DgnFile *) 
 from DgnPlatform.lib (dgnFileObj_getHighestElementID@Bentley@@YA_KPEAUDgnFile@DgnPlatform@1@@Z)? 
 my .fdf looks like that: 
 BEGIN_BENTLEY_NAMESPACE

unsigned __int64 dgnFileObj_getHighestElementID(struct Bentley::DgnPlatform::DgnFile*);

END_BENTLEY_NAMESPACE 
 when i try to call, an (linker) error appears: 
 Error LNK2028: unresolved token (0A0000DA) "extern "C" unsigned __int64 __cdecl dgnFileObj_getHighestElementID(struct Bentley::DgnPlatform::DgnFile *)" (?dgnFileObj_getHighestElementID@@$$J0YA_KPEAUDgnFile@DgnPlatform@Bentley@@@Z) referenced in function "public: virtual __int64 __clrcall Hsi::Asw::Interop::Graphics::Model::GetHighestElementId(void)" (?GetHighestElementId@Model@Graphics@Interop@Asw@Hsi@@$$FUE$AAM_JXZ) 
 Error LNK2019: unresolved external symbol "extern "C" unsigned __int64 __cdecl dgnFileObj_getHighestElementID(struct Bentley::DgnPlatform::DgnFile *)" (?dgnFileObj_getHighestElementID@@$$J0YA_KPEAUDgnFile@DgnPlatform@Bentley@@@Z) referenced in function "public: virtual __int64 __clrcall Hsi::Asw::Interop::Graphics::Model::GetHighestElementId(void)" (?GetHighestElementId@Model@Graphics@Interop@Asw@Hsi@@$$FUE$AAM_JXZ) 
 
 thanks for any idea. 
 
 Best regards 
 Jan

Robert Hook · Answer

Hi Jan Vágner , 
 Jan Vágner said: we use this function in v8i for getting highest element id in model for our non graphic data solution purposes. 
 As others suggested, using an unpublished function is not highly recommended. 
 Unfortunately this response does not provide enough insights into the problems/challenges (tasks/workflows) your code is attempting to resolve. If you could expand a bit on the conditions/workflows for why you (think you may) need to call dgnFileObj_getHighestElementID we may be able to provide the best recommendation possible. Using that function you (and your app) can get some unexpected results quickly (or what may appear sporadically) if you are not careful. 
 I suspect you are attempting to use a ForeignID to map to MicroStation ElementIDs; where if a user uses any Bentley product tools to modify those elements; the ElementID (unfortunately) is not a contract that the same element/component will maintain that exact same ID for the complete lifecycle of the component's life; and in a number of cases/workflows *will* be reassigned. If you do have your own component id solution (a.k.a. a ForeignID) that you wish to ensure consistently correct MicroStation component element IDs will be returned, I suggest taking a look at the MicroStationAPI.chm help file topic: ElementIDMap (Header: include\DgnPlatform\ElementIdMap.h). Although the SDK currently does not provide an example for this API, there is a very helpful code snippet in the help topic ElementIDMap (See: Detailed Description). 
 For the signature of an unpublished function you need to ensure an exact/correct function signature is being declared and provided. Otherwise the declaration though looking correct is still likely never be called. From your results, the .DLL output would appear closest to what the underlying declaration (if properly qualified w/MicroStation - namespaces and types) would likely look something like: 
 ElementId Bentley::dgnFileObj_getHighestElementID (DgnFileP pFile) 
 So, let me know if ElementIDMap is the solution you are really looking to implement, or some more information related to your workflows related to calling dgnFileObj_getHighestELementID; in case other options/solutions may be available. 
 HTH, Bob

Jon Summers · Answer

Jan Vágner said: is there any way, how to call undocumented function 
 Generally, undocumented functions are not supported: don't use them. That is, it's signature could change, it might be dropped in favour of something else, or it could become forgotten and broken if not used for anything by MicroStation. 
 MicroStation allocates object IDs automatically. We can't assign them: only read them. 
 Having provided that cautionary note, I ask why you want to use dgnFileObj_getHighestElementID() ? 
 Compiler or Linker Error? 
 You ask how to call that function, which you've done successfully: you don't have a C++ compiler error. The errors you have posted (LNK2028 and LNK2019) are from the C++ linker, not the compiler. The message is clear: the linker can't find the definition of the function. That is, the compiled binary code was not found. 
 You'll have to search the delivered library ( *.lib ) and implementation ( *.dll ) files to find it. How do you do that? That question has been asked and answered many times. Search web sites that deal with Microsoft technology. Here's one example .

Paul Chater · Answer

Hi, 
 Call DgnFile::GetHighestID. The dgnFileObj_ function just calls that with the dgnfile pointer you pass in. 
 
 Paul

[CONNECT C++] Calling undocumented function dgnFileObj_getHighestElementID

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