用LINQ查询分组数据

我有一个C＃DataTable，里面有5列。我只关心DataTable中的两列。我关心的两列称为“CreateDate”和“ID”。它们是DateTime和字符串。 DateTime表示票据提交的日期。该ID唯一代表一张票。用LINQ查询分组数据

我想写一个LINQ语句，显示每个日期创建的票数。但是，我无法弄清楚这是如何做到的。有人可以告诉我如何做到这一点？

谢谢！

来源

2010-07-24 user336786

我相信这样的事情会工作：

var result = from ticket in TicketTable 
group ticket by ticket.CreateDate.Date into g 
select new {Date = g.Key, Count = g.Count() };

来源

2010-07-24 20:55:13 recursive

+1。正确的解决方案，假设'CreateDate'不包含确切的时间。 – 2010-07-24 21:05:29

CreateDate是一个完整的DateTime对象。这怎么解决？ – user336786 2010-07-24 21:06:41

我的解决方案使用.Date 处理该问题http://msdn.microsoft.com/en-us/library/system.datetime.date.aspx – recursive 2010-07-24 21:09:37

class Program 
{ 
    static void Main(string[] args) 
    { 
     List<Ticket> tickets = new List<Ticket>(); 

     tickets.Add(new Ticket() { CreateDate = DateTime.Now, Id = 1 }); 
     tickets.Add(new Ticket() { CreateDate = DateTime.Now.AddDays(1), Id = 2 }); 
     tickets.Add(new Ticket() { CreateDate = DateTime.Now.AddDays(1), Id = 3 }); 
     tickets.Add(new Ticket() { CreateDate = DateTime.Now.AddDays(2), Id = 4 }); 
     tickets.Add(new Ticket() { CreateDate = DateTime.Now.AddDays(2), Id = 5 }); 
     tickets.Add(new Ticket() { CreateDate = DateTime.Now.AddDays(3), Id = 6 }); 
     tickets.Add(new Ticket() { CreateDate = DateTime.Now.AddDays(3), Id = 7 }); 
     tickets.Add(new Ticket() { CreateDate = DateTime.Now.AddDays(4), Id = 8 }); 
     tickets.Add(new Ticket() { CreateDate = DateTime.Now.AddDays(5), Id = 9 }); 
     tickets.Add(new Ticket() { CreateDate = DateTime.Now.AddDays(6), Id = 10 }); 
     tickets.Add(new Ticket() { CreateDate = DateTime.Now.AddDays(7), Id = 11 }); 

     var query = tickets. 
        GroupBy(t => t.CreateDate.Date). 
        Select(g => new { Date = g.Key, Count = g.Count() }); 

     foreach (var g in query) 
     { 
      Console.WriteLine("{0} - {1}", g.Date, g.Count); 
     } 

     /* Outputs: 
      7/24/2010 12:00:00 AM - 1 
      7/25/2010 12:00:00 AM - 2 
      7/26/2010 12:00:00 AM - 2 
      7/27/2010 12:00:00 AM - 2 
      7/28/2010 12:00:00 AM - 1 
      7/29/2010 12:00:00 AM - 1 
      7/30/2010 12:00:00 AM - 1 
      7/31/2010 12:00:00 AM - 1 */ 
    } 

    class Ticket 
    { 
     public int Id { get; set; } 
     public DateTime CreateDate { get; set; } 
    } 
}

来源

2010-07-24 21:08:22

用LINQ查询分组数据

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