Question

我有一个简单的清单

T.Date = 11/04/2014，T.Title =“Book1”，T.Tipology =“Book”

T.Date = 14/04/2014，T.Title =“Book2”，T.Tipology =“Book”

T.Date = 02/05/2015，T.Title =“Spot1”，T.Tipology =“Spot”

T.Date = 21/06/2015，T.Title =“Newspaper1”，T.Tipology =“Newspaper”

我需要按年份，月份和日期对此列表进行分组，如下所示：

2014

四月

T.Date = 11/04/2014，T.Title =“Book1”，T.Tipology =“Book”

T.Date = 14/04/2014，T.Title =“Book2”，T.Tipology =“Book”





2015

五月

T.Date = 02/05/2015，T.Title =“Spot1”，T.Tipology =“Spot”



六月

T.Date = 21/06/2016，T.Title =“Newspaper1”，T.Tipology =“Newspaper”

所以我将能够在foreach函数中处理数据，如：

 foreach(var year in Year)
 {
     foreach(var month in Month)
     {
         foreach(var day in Day)
         {
            Console.WriteLine(day.Item.Title);
            Console.WriteLine(day.Item.Tipology);
         }
         Console.WriteLine(month.ToString()); // With culture
     }
     Console.WriteLine(year.ToString());
 }

我如何用（c＃）LINQ做到这一点？

Answer 1

您可以按年，月和日订购它们：

$sp = New-Object -TypeName Microsoft.SqlServer.Management.SMO.StoredProcedure -argumentlist $db, "GetUserPhoneForService"

如果您真的想将它们分组，那么您可以执行以下操作：

var sorted = list.OrderBy(x=>x.Date.Year)
                 .ThenBy(x=>x.Date.Month)
                 .ThenBy(x=>x.Date.Day);

因此它会为您提供每年月份日期的分组数据

Answer 2

您可以使用嵌套组。

var groups = list
            .GroupBy(
                    d => d.Date.Year, 
                    (key, g) => g.GroupBy(
                                          d => d.Date.Month,
                                          (key2, g2) => g2.GroupBy(d => d.Date)
                                         )
                    );

Answer 3

您的对象可以继承IComparable，而不仅仅是您的对象。

Answer 4

您可以订购列表，然后跟踪上一本书：

var orderedBooks = books.OrderBy(x => x.Date.Year).ThenBy(x => x.Date.Month).ThenBy(x => x.Date.Day);
Book last = null;
foreach (Book book in orderedBooks)
{
    Console.WriteLine(book.Title);
    Console.WriteLine(book.Tipology);
    if(last != null  && last.Date.Month != book.Date.Month)
        Console.WriteLine(DateTimeFormatInfo.CurrentInfo.GetAbbreviatedMonthName(book.Date.Month)); // With culture
    if (last != null && last.Date.Year != book.Date.Year)
        Console.WriteLine(book.Date.Year.ToString()); 
    last = book;
}

LINQ - 组列表<t>到年，月，日

4 个答案: