是否可以使用LINQ进行动态调整？

Question

我有一个T-SQL 2005查询返回:

pid         propertyid  displayname     value
----------- ----------- --------------- ---------------
14270790    74          Low Price       1.3614
14270790    75          High Price      0
14270791    74          Low Price       1.3525
14270791    75          High Price      0
14270792    74          Low Price       1.353
14270792    75          High Price      0
14270793    74          Low Price       1.3625
14270793    75          High Price      0
14270794    74          Low Price       1.3524
14270794    75          High Price      0

我想做的主要是在displayname球场上转移,希望产生:

pid       Low Price  High Price
14270790  1.3614     0
14270791  1.3525     0
14270792  1.353      0
14270793  1.3625     0
14270794  1.3524     0

(不确定如何输出propertyid字段,所以我把它遗漏了(希望它只是与低价和高价字段并排,以表明它们的ID,但我认为这不会起作用.)

问题是,原来的内容displayname领域是动态的-它是从一个与联接生产PropertyName' table, so the number of pivoted columns is variable. It could therefore contain高价格,低价格,打开andClose`,这取决于与该表返回加入.

这是当然的,相对容易(无论我在写初始查询的麻烦!)在一个固定的查询或存储过程来产生这种转动.但是,是有可能得到LINQ生成的SQL查询这将名字而产生的每一列不必编写动态(可能在一个存储过程)查询,其中列出了列名？

谢谢,

马特.

Answer 1

我会给你一个带有不同数据的样本(我需要的).您可以根据需要进行调整.请注意,只使用了两个linq查询,其他大部分都是将列表转换为数据表.

         var data = new[] {
                new{Student=1, Subject="English", Marks=40},
                new{Student=1, Subject="Maths", Marks=50},
                new{Student=1, Subject="Science", Marks=60},
                new{Student=1, Subject="Physics", Marks=70},
                new{Student=1, Subject="Chemistry", Marks=80},
                new{Student=1, Subject="Biology", Marks=90},
                new{Student=2, Subject="English", Marks=4},
                new{Student=2, Subject="Maths", Marks=5},
                new{Student=2, Subject="Science", Marks=6},
                new{Student=2, Subject="Physics", Marks=7},
                new{Student=2, Subject="Chemistry", Marks=8},
                new{Student=2, Subject="Biology", Marks=9}
            };

        /*Here the pivot column is the subject and the static column is student
        group the data against the static column(s)*/

        var groups = from d in data
                     group d by d.Student into grp
                     select new
                     {
                         StudentId = grp.Key,
                         Marks = grp.Select(d2 => new { d2.Subject, d2.Marks }).ToArray()
                     };


        /*get all possible subjects into a separate group*/
        var subjects = (from d in data
                        select d.Subject).Distinct();

        DataTable dt = new DataTable();

        /*for static cols*/
        dt.Columns.Add("STUDENT_ID");


        /*for dynamic cols*/
        foreach (var subject in subjects)
        {
            dt.Columns.Add(subject.ToString());
        }

        /*pivot the data into a new datatable*/
        foreach (var g in groups)
        {
            DataRow dr = dt.NewRow();
            dr["STUDENT_ID"] = g.StudentId;

            foreach (var mark in g.Marks)
            {
                dr[mark.Subject] = mark.Marks;
            }
            dt.Rows.Add(dr);
        }