linq 实现group by 不使用group关键字 等同lambad表达式中的group join 查询一对多关系

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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

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