Linq to Entities 一对多外键关联 添加数据报错？该怎么解决

Linq to Entities 一对多外键关联 添加数据报错？
ActilceT At = new ActilceT();
  At.ActicleContent = "ss";
  At.ActilceListT.ActilceListID = 1;//这行报错未将对象引用到实例；ActilceListID是ActilceT表的外键，ActilceListT是主表，
  using (E_dbEntities db = new E_dbEntities())
  {
  db.AddToActilceT(At);
  db.SaveChanges();
  }

------解决方案--------------------------------------------------------

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ActilceT At = new ActilceT();
At.ActicleContent = "ss";
At.ActilceListT.ActilceListID = 1;//这行报错未将对象引用到实例；ActilceListID是ActilceT表的外键，ActilceListT是主表，
using (E_dbEntities db = new E_dbEntities……

------解决方案--------------------------------------------------------
At.ActilceListT=new 类型；
At.ActilceListT.ActilceListID = 1;