Question

我有一个这样的行列表（因为我使用的是DefaultIfEmpty，所以是NULL）

Vol           Component         Dwg      View    Revision   

Volume U01  Composed Drawings   SJTest  1   B
Volume U01  Composed Drawings   SJTest  1   A
Volume U01  Composed Drawings   SJTest  1   NULL
Volume U03  Composed Drawings   SJTest2 2   NULL

我想按每个组的最后一个coln（A，B，NULL）排序，然后只得到第一行。所以在这种情况下，我应该将最终设置为：

Volume U01  Composed Drawings   SJTest  1   B
Volume U03  Composed Drawings   SJTest2 2   NULL

有什么想法？我迷失了如何从分组中获得这一点 - 每组的第一行。

这是LINQ-SQL ...对不起忘了。

感谢苏尼特

Answer 1

因为你说第一组的第一行应该是修订版“B”，我猜你想按降序排序，所以这样的事情呢？

var query = yourData
            .GroupBy(x => new { x.Vol, x.Component, x.Dwg, x.View })
            .Select(g => g.OrderByDescending(x => x.Revision).First());

// and to test...
foreach (var x in query)
{
    Console.WriteLine("{0}\t{1}\t{2}\t{3}\t{4}",
        x.Vol, x.Component, x.Dwg, x.View, x.Revision ?? "NULL");
}

// Volume U01    Composed Drawings    SJTest     1    B
// Volume U03    Composed Drawings    SJTest2    2    NULL

linq从一组返回单行

1 个答案: