AutoCAD .Net 禁止图元被删除

禁止图元被用户删除可以通过 ObjectOverrule 实现。
以下代码:
1、命令 AddEraseOverrule 创建两个图元并禁止被删除。
2、命令 RemoveEraseOverrule 移除删除限制。

static EraseOverrule eraseRule = null;public class EraseOverrule : ObjectOverrule{    public override void Erase(DBObject dbObject, bool erasing)    {        throw new Autodesk.AutoCAD.Runtime.Exception(               Autodesk.AutoCAD.Runtime.ErrorStatus.NotApplicable);        //base.Erase(dbObject, erasing);    }}[CommandMethod("AddEraseOverrule")]public static void AddEraseOverrule(){    if (eraseRule == null)    {        eraseRule = new EraseOverrule();        Overrule.AddOverrule(RXObject.GetClass(typeof(Entity)),                             eraseRule, true);        Overrule.Overruling = true;        eraseRule.SetIdFilter(CreateEntities());    }}[CommandMethod("RemoveEraseOverrule")]public static void RemoveEraseOverrule(){    if (eraseRule != null)    {        Overrule.Overruling = false;        Overrule.RemoveOverrule(RXObject.GetClass(typeof(Entity)),                                eraseRule);        eraseRule.Dispose();        eraseRule = null;    }}private static ObjectId[] CreateEntities(){    Document doc = Application.DocumentManager.MdiActiveDocument;    Database db = doc.Database;    ObjectId[] oids = new ObjectId[2];    using (Transaction tr = db.TransactionManager.StartTransaction())    {        BlockTableRecord space = tr.GetObject(db.CurrentSpaceId, OpenMode.ForWrite) as BlockTableRecord;        //        Line line = new Line();        line.StartPoint = new Point3d(0, 0, 0);        line.EndPoint = new Point3d(100, 100, 0);        space.AppendEntity(line);        tr.AddNewlyCreatedDBObject(line, true);        oids[0] = line.ObjectId;        //        Circle circle = new Circle();        circle.Center = new Point3d(0, 0, 0);        circle.Radius = 50;        space.AppendEntity(circle);        tr.AddNewlyCreatedDBObject(circle, true);        oids[1] = circle.ObjectId;        tr.Commit();    }    return oids;}

1、类 EraseOverrule 继承自 ObjectOverrule，并重写了 Erase 方法。
在该方法中，通过抛异常而不是执行删除操作，禁止图元被删除。

2、SetIdFilter 确保该规则只对特定 ObjectId 的图元有效。
ObjectOverrule 还有方法 SetXDataFilter，可以用来设置只对拥有特定 XData 的对象有效。

参考文章：
Prevent deletion/erasing of entity