This is hints of Code to Get dimension description and value in ax 2012. I have taken example of purchase order to show by selection first line of purchase line dimension value and description.
PurchLine _purchLine;
DimensionValue _Dimvalue;
Description _Dimdesc;
;
select firstonly _purchLine;
_Dimvalue= dimValue(_purchLine.DefaultDimension, 'Department');
_Dimdesc = dimDesc(s_purchLine.DefaultDimension, 'Department');
info(strfmt("%1: %2", _Dimvalue, _Dimdesc));