[Dcmlib] 0008 0070 Recognition code

[Luca Picello]

I do not have a clear idea on what is gdcm philosophy and i am trying to 
learn it from examples.
Can someone please explain to me what is the difference between:

gdcm::DicomDir *e1;
e1 = new gdcm::DicomDir( folder , true );
std::string ssss = e1->GetEntryValue(0x0008,0x0070);

and

gdcm::File *f1= new gdcm::File( filename );
f1 = new gdcm::DicomDir( fold.c_str() , true );
std::string ssss = f1->GetEntryValue(0x0008,0x0070);

it seems that if I try to access to the "directory" map of dicom tags it 
does not work.
instead working on a single file it works.why?
thank you,

Luca