Question

你们如何将这个查询转换为Linq？

SELECT *
FROM Test T1
WHERE  (convert(VARCHAR,T1.IdVersFirmFuente) + convert(VARCHAR,T1.IdVersLib)) 
IN 
(
      Select TOP 1 convert(VARCHAR,T2.IdVersFirmFuente) + convert(VARCHAR,T2.IdVersLib)
      From Test T2
      Where T2.IdVersFirmFuente = T1.IdVersFirmFuente
      ORDER BY T2.CodVersion DESC
)

它应该是这样的：

var Resul = (from u in nDT2.AsEnumerable()
            where (String.Concat(u.Field<int>("IdVersionLibreria").ToString(),u.Field<int>("IdVersionFirmwareFuente").ToString()))
                    .Contains(
                        (from y in nDT2.AsEnumerable()
                        where y.Field<int>("IdVersionFirmwareFuente") == u.Field<int>("IdVersionFirmwareFuente")
                        orderby y.Field<String>("CodVersion") descending
                        select String.Concat(y.Field<int>("IdVersionLibreria").ToString(),y.Field<int>("IdVersionFirmwareFuente").ToString())
                        ).Take(1))
            select u);

目的是让那些独特的“IdVersFirmFuente”拥有最高的CodVersion（如果有很多）

IdVersFirmFuente IdVersLib IdVersion CodVersion
==
236              628       628       1.0.0.0
236              629       629       1.0.0.1
237              628       628       1.0.0.0
239              628       628       1.0.0.0

结果将是：

236              629       629       1.0.0.1
237              628       628       1.0.0.0
239              628       628       1.0.0.0

提前致谢。

Answer 1

我认为你让事情变得比实际更复杂。根据您的样本数据判断，您只需要按IdVersFirmFuente对行进行分组，按CodVersion对每个组进行排序，并从每个组中选择第一个元素。像这样：

class Program
{
    public class Row
    {
        public int IdVersFirmFuente { get; set; }
        public int IdVersLib { get; set; }
        public int IdVersion { get; set; }
        public string CodVersion { get; set; }
    }

    static void Main()
    {
        var data = new[]
                       {
                           new Row { IdVersFirmFuente = 236, IdVersLib = 628, IdVersion = 628, CodVersion = "1.0.0.0" },
                           new Row { IdVersFirmFuente = 236, IdVersLib = 629, IdVersion = 629, CodVersion = "1.0.0.1" },
                           new Row { IdVersFirmFuente = 237, IdVersLib = 628, IdVersion = 628, CodVersion = "1.0.0.0" },
                           new Row { IdVersFirmFuente = 239, IdVersLib = 628, IdVersion = 628, CodVersion = "1.0.0.0" }
                       };

        var result = from u in data
                     group u by u.IdVersFirmFuente into g
                     select g.OrderByDescending(e => e.CodVersion).First();

        foreach (var row in result)
        {
            Console.WriteLine("{0,-5}{1,-5}{2,-5}{3,-10}", row.IdVersFirmFuente, row.IdVersLib, row.IdVersion, row.CodVersion);
        }
    }
}

将带有两列的SQL IN子句转换为LINQ

1 个答案: