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。