ref BillStatus? State 这个是什么意思？

Question

在BillStatus中是没有State 的啊？  using (FlowDbContext db = CreateContext(trans))             {                 BillStatus? state = null;                 db.Submit(                     billTypeId,                     billId,                     flowId,                    ref state                 );                return state.Value;             }    public enum BillStatus     {        /// <summary>         /// 已提交未审核        /// </summary>         Submited = 1,        /// <summary>         /// 已经审核，但未完成        /// </summary>         Processing = 2,        /// <summary>         /// 通过流程的        /// </summary>         Passed = 3,        /// <summary>         /// 被否决的        /// </summary>         Rejected = 4     }

Answer 1

ref进去了被改了啊