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Person_Addresses我有 Person 实体,它与(字段:PersonID、、、AddressID)具有 1:N 关系ValidFrom。我想获取所有Person记录并Person_Addresses仅与最新的 ValidFrom 相关联。我应该如何使用 ObjectQuery 或 IQueryable 执行此操作?

编辑: 我提到ObjectQueryand IQueryable,因为我想有一个使用扩展方法的解决方案(我认为,它是如何被调用的)。另外我忘了提到我正在使用生成实体的实体框架。我想得到一个 person 对象,它的 person_adress 成员急切地加载。

以下是实体结构: 个人成员:int id、字符串名字、字符串姓氏、Partner_Address partneradress

Person_Address 成员:int personid, int adressid,date validfrom

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1 回答 1

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试试下面的。

我有以下实体。

    //Person Entity
    public class Person
    {
        public int PersonID  { get; set; }
        public string PersonName { get; set; }
    }

    //PersonAddress Entity
    public class PersonAddress
    {
        public int PersonID { get; set; }
        public int AddressID { get; set; }
        public DateTime ValidFrom { get; set; }
    }

然后触发以下查询。

    //Get the latest ValidFrom for each person from PersonAddress.
    var getLatestDateRecords =
    from p in lstPersonAddress
    group p by p.PersonID into g
    select new
    {
        Infos =
            (from PA in g
            select new
            {
                PersonId = PA.PersonID
                Date = g.Max(t=>t.ValidFrom)
            }).Distinct()
    };

    //Segregate the ValidFroms and PersonId from the
    //previous record set(getLatestDateRecords).
    var segRecords =
        from x in getLatestDateRecords
        from y in x.Infos
        select new { Date = y.Date, PersonId = y.PersonId };

    //Obtain all the relevant information from the PersonAddress
    // for the latest ValidFrom dates.
    var allValidRecords =
        from PA in lstPersonAddress
        join x in segRecords
        on PA.ValidFrom equals x.Date
        where PA.PersonID == x.PersonId
        select new {
                PersonId = PA.PersonID
                , AddressId = PA.AddressID
                , Date = PA.ValidFrom
            };

    //Get the final result
    var resultSet =
        from p in lstPerson
        join x in allValidRecords
        on p.PersonID equals x.PersonId
        select new
        {
            PersonId = p.PersonID
            ,PersonName = p.PersonName
            ,AddressId = x.AddressId,
            Date = x.Date
        };

我发现它可以很好地处理一些测试数据。

如有任何疑问,请告诉我。

于 2010-06-22T13:23:49.803 回答