[quote user="Frode Tørresdal"]I would rather not have any memory leakage[/quote]
Me neither! I notice that there is a tag value class DgnTagValue, declared in header DgnPlatform.r.h. That class is richer than the TagValue struct in V8i, as it includes methods as well as data.
There is method DgnTagValue.ClearCurrentValue(). Help tells us that it 'clears the current value'. That could mean that it frees string and binary memory. But it would be nice to know for sure. If so, that would make mdlTag_freeValue redundant.
mdlTag_create and mdlTag_extract both take a DgnTagValueP rather than a TagValue*.