写linq similiar在sql查询

Question

如何使用来自SELECT

的linq WHERE spesific_field条IN在SELECT中撰写|   absent | | lab | | time | |———————————————| |———————————————| |———————————————| |PK| absentID | ┌————|PK| labID | ┌————|PK| timeID | | | date      | | | | class_room | | | | start | |FK| labID |———┘   | | timeID |—————┘ | | finish |

架构表

SELECT  COUNT(*)
FROM    absent
WHERE   labID IN ( SELECT  lab.labID
                   FROM    lab INNER JOIN time
                           ON lab.timeID = time.timeID
                   WHERE   lab.class_room = @class_room AND
                           time.start => getdate() and getdate() <= time.finish 

如果它是用与此类似的查询代码编写的

[DataContract]
    public class absent
    {
        [DataMember]
        public int absentID { get; set; }

        [DataMember]
        public string name{ get; set; }

        [DataMember]
        public lab labID { get; set; }
    }
}

[DataContract]
    public class lab
    {
        [DataMember]
        public int LabID{ get; set; }

        [DataMember]
        public string class_room { get; set; }

        [DataMember]
        public time timeID { get; set; }
    }
}

[DataContract]
    public class time
    {
        [DataMember]
        public int timeID { get; set; }

        [DataMember]
        public DateTime start { get; set; }

        [DataMember]
        public DateTime finish{ get; set; }
    }
}

  

[edit] [班级模特]

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Answer 1

假设您已从db中检索了一个包含所有引用对象的完整模型，它看起来像您想要的那样：

        string someClassRoom = null;                //put classroom here
        DateTime someDateTime = default(DateTime);  //put date here
        List<absent> absentCollection = null;       //your collection or db table here
        int count = absentCollection
            .Where(abs => 
                abs.labID.class_room == someClassRoom && 
                abs.labID.timeID.start >= someDateTime && 
                someDateTime <= abs.labID.timeID.finish)
            .Count();