Not entirely necessary to use .Net for this. The AnnoScale is saved as an extension dictionary to the view object. The VL stuff only gets you so far (Adesk "decided" to stop updating the ActiveX library some time back). For the rest you need to look into the raw DXF data. E.g. this would extract the anno scale's name from the view name:
Code:
(vl-load-com)
(defun GetViewAnnoScale (ViewName / view xDict annoScale)
(if (not (vl-catch-all-error-p
(setq view (vl-catch-all-apply
'vla-Item
(list (vla-get-Views (vla-get-ActiveDocument (vlax-get-acad-object))) ViewName)))))
(if (and (eq (vla-get-HasExtensionDictionary view) :vlax-true)
(setq xDict (vla-GetExtensionDictionary view))
(not (vl-catch-all-error-p (setq annoScale (vl-catch-all-apply 'vla-Item (list xDict "ADSK_XREC_VTR_ANNOSCALE_DATA"))))))
(cdr (assoc 300 (entget (cdr (assoc 340 (entget (vlax-vla-object->ename annoScale))))))))))