将objectidde的oldid以int32格式保存在xrecord中,
TypedValue tv = new TypedValue((int)DxfCode.Int32, sourceEnt.ObjectId.OldId);
Xrecord xRec = new Xrecord();
xRec.Data = new ResultBuffer(tv);
将xrecord保存在你想要的位置
用的时候读取出来,然后create a objectid
ObjectId sourceMtextId = new ObjectId(idNum);