I have a number of Acgeentities,but no sort，and Do not know who is and who is connected；
it can be this
or like this：
and so on.....
next i want creat a acdbhatch
You will clearly need to know the boundary to create a hatch or let AutoCAD determine the boundary using the "BOUNDARY" command by providing a point inside the closed area.
From what you have described, you may need to traverse all the entities and write some algorithm that compares their end points and determines closed loops. After you have identified the boundary loops, the hatches can be created.
Hope this helps.
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