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Not sure what your ultimate goal is: do you want to permanently draw hatches over each Parcel and set the hatch color based on the area; or these colored hatches are only needed temporarily in a certain CAD process? That is, what is the purpose to create hatches on top of each parcel? You might create different Parcel styles (with different area fill configured) and use code to assign certain styles to the parcels based on their area.
In the case you must draw hatches on top of the parcels for certain reason(s), exploding the parcel would only work if the parcel style's area fill is set to be visible. If the area fill is not visible, the exploded DBObject is a closed polyline, and you need to create the hatch from this polyline. Because of this, I'd not do exploding. Instead, I'll use Parcel.BaseCurve property to obtain a closed polyline and create the hatch. Again, I do not know why you want to place hatches on top of parcels while the parcels can be easily colored/filled with different styles.
Well, for the sake of sticking with your logic (exploding each Parcel object to get a Hatch and its area, then determine the color of the hatch), I do not see why you need to store the parcel location and its size(area) and match the parcels and hatches later. You can simply loop through the Parcel ObjectIdCollection obtained from Site.GetParcelIds() (pseudo code):
using (var tran = [start transaction])
{
var parcelIds=[site].GetParcelIds();
foreach (ObjectId id in parcelIds)
{
var parcel=(Parcel)tran.GetObject(id,....);
var area=parcel.Area;
var hatch=ExplodeTheParcel(parcel);
var colorIndex=DetermineRequiredColor(area);
// Then you can set the hatch's color
// add the hatch to the database/modelspace
}
tran.Commit();
}
Of course, as I previously said, if the parcel's style is set to not show its fill, then the exploding would not give you a hatch. So, I'd prefer creating the hatch based on the Parcel's BaseCurve instead of exploding. As side benefit, you would not run into the missing "area" issue at all. Or, maybe a different option, you could also try to create MPolygon instead of Hatch?
Perhaps I'm not exploding correctly, but the only hatch I get when exploding a Parcel is the background mask for the ParcelAreaLabel. If I use a label set to not display anything, no hatch is in the exploded objects collection. So how, exactly, is a Parcel exploded with the fill hatch?
I agree with @norman.yuan that the hatch should be created from the BaseCurve of the Parcel.
As the Parcel Style editing dialog shows, if the "Parcel Area Fill" is set to not visible (which is default), then exploding a parcel would not create a Hatch. so, if the OP want to go with the exploding approach, he/she have to make sure the "Parcel Area Fill" is turned on.
@norman.yuan With the area fill turned on in the style in use, the only hatch I get is the background mask of the label. (Civil 3D 2023) Tried with a Solid fill and a standard hatch pattern.
See attached video clip, showing how exploding parcel could generate different entities, depending on the parcel style. Note, running command "Explode" against Parcel is much like the API call of Blockreference.ExplodeToOwnerSpace(), that is, besides generating element entities, the parcel itself remain unchanged, while the command in plain AutoCAD erases the original entity to be exploded.
@norman.yuan Thanks, and yes, I understand all that. Performing the explode in code does not give me that result. I only add the Hatch object to the drawing and color is green. It is the same as the background mask for the label, there is no hatch for the overall parcel.
If you can get the full hatch, what am I doing wrong?
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