To Get Primary key field name of table in axapta by code you can try following code.
First you need to declare variable for dictTable .
First you need to declare variable for dictTable .
DictTable _dictTable;
DictField _dictField;
;
_dictTable = new SysDictTable(tableNum(SalesTable));
// Then you need to call primary key field by passing table id like here we have pass salestable and dicttable.id() method will get id of salestable.
_dictField = new SysDictField(dictTable.id(), dictTable.primaryKeyField());
info(dictField.name());