return from orderInfo in orderEntity.x_s_orderInfo                      join oState in orderEntity.x_s_oStatuInfo                                       on orderInfo.oId equals oState.oId into t                                            select new OrderInfoModel                      {                         orderInfo= orderInfo,                         // UserIDs = string.Join(",", t.Select(x => x.UserID.ToString()).ToArray())                      };

　　关键在于 into 

查询一对多关系

/// <summary>

/// 订单状态信息

/// </summary>

public IEnumerable<x_s_oStatuInfo> orderState { get; set; }

这里将订单状态改为集合类型

select new OrderInfoModel                      {                         orderInfo= orderInfo,                    orderState=t.Select(u=>u)                      };