将实体添加到集合中的方法

// 创建圆
AddCircle(new Point3d(0, 0, 0), 6);
AddCircle(new Point3d(0, 0, 0), 8);
public static void AddCircle(Point3d cenPt, double radius)
{
       Database db = HostApplicationServices.WorkingDatabase;
       using (Transaction tr = db.TransactionManager.StartTransaction())
       {
         BlockTable bt = (BlockTable)tr.GetObject(db.BlockTableId, OpenMode.ForRead);
         BlockTableRecord btr = (BlockTableRecord)tr.GetObject(bt[BlockTableRecord.ModelSpace], OpenMode.ForWrite);
         Circle cr = new Circle(cenPt, Vector3d.ZAxis, radius);
         btr.AppendEntity(cr);
         tr.AddNewlyCreatedDBObject(cr, true);
         tr.Commit();
       }
}