I'm confused as to which tags need to be examined to determined if a Mammo image is MLO or CC.
On sample sets I have I see the relevant information in View Position(0018,5101) i.e. a value of "MLO".
However looking at the standard it refers to Partial View Code Sequence (0028,1352) which is a sequence and there are more than just MLO/CC values.
The correct tag to check is the View Code Sequence, not the Partial View Code Sequence (that is only for partial views, as the name suggests, which seems not to be your case). In the sequence, you have to check the Code Value for the respective code. For example, MLO images get the code R-10226, as can be seen in the table.
Only if that sequence is not present or empty, you have to check for fallback tags like View Position. View Position is defined for CR and DX images, not for MG images (and actually does not have MLO or CC as defined terms), but as always, derivations from the DICOM standard by some modalities have to be taken into account, and you have to check if the images you process conform to the standard.