BricsCAD V18 is able to recreate the boundary.
Judging from the file version you are using AutoCAD 2004-2006. Maybe newer versions of that program can cope with this as well?
I want the result is that the boundary type is region,not polyline.
When using below cods in autocad2007,the result is ok. But in autocad2018/2018, it do nothing.
(vl-cmdf "-hatchedit" (car(entsel)) "b" "r" "n").