无法在按linq分组后保留属性

本文关键字：保留 属性 linq | 更新日期: 2023-09-27 18:12:02

我有一个用法集合，如下所示，需要如下输出:

这是我的用法类:

public class Usage
{
    public Usage()  {}
    public string Alias { get; set; }
    public int ActivityCount { get; set; }
    public DateTime HitDate { get; set; }
}

这是我的代码:

我想首先将集合分组为Users，对于每个用户，我想获得每天的点击次数，如下面的EXPECTED输出所示。请注意，日期时间a和d是同一天的不同时间，因此需要将它们分组在一起。

我将用它来绘制点击量与日期的柱状图，即每天点击量

在这样做时，我无法将别名字段数据保存到我的第二级分组中:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading.Tasks;
namespace NullOperator
{
    class Program
{
    static void Main(string[] args)
    {
        var a = new DateTime(2015, 10, 23, 12, 05, 06);
        var b = new DateTime(2015, 10, 24, 12, 05, 06);
        var c = new DateTime(2015, 10, 25, 12, 05, 06);
        var d = new DateTime(2015, 10, 23, 14, 05, 06);
        var usages = new List<Usage>
        {
            new Usage{Alias = "A ",HitDate = a},
            new Usage{Alias = "A ",HitDate = a},
            new Usage{Alias = "A ",HitDate = d},
            new Usage{Alias = "A ",HitDate = b},
            new Usage{Alias = "A ",HitDate = b},
            new Usage{Alias = "A ",HitDate = b},
            new Usage{Alias = "A ",HitDate = c},

            new Usage{Alias = "B ",HitDate = a},
            new Usage{Alias = "B ",HitDate = b},
            new Usage{Alias = "B ",HitDate = b},
            new Usage{Alias = "B ",HitDate = c},
            new Usage{Alias = "B ",HitDate = c},
            new Usage{Alias = "B ",HitDate = c},
            new Usage{Alias = "C ",HitDate = a},
            new Usage{Alias = "C ",HitDate = a},
            new Usage{Alias = "C ",HitDate = a},
            new Usage{Alias = "C ",HitDate = c},
            new Usage{Alias = "C ",HitDate = c},
            new Usage{Alias = "C ",HitDate = c},
        };
        var g = usages.GroupBy(r => r.Alias);
        foreach (var u in g)
        {          
            var x = u.GroupBy(r => r.HitDate.Day).Select(gr=>new
            {
                HitDate=gr.Key,
                Count=gr.Count()
            });
            foreach (var m in x)
            {
                Console.WriteLine(m.HitDate + "  " +m.Count);
            }
        }
        Console.Read();
    }
}

//期望输出

Alias : HitDate.Date  : hitcount
//  A  - 23/10/2015  - 3
//  A  - 24/10/2015 - 3
//  A  - 25/10/2015 - 1
//  B  - 23/10/2015 - 1
//  B  - 24/10/2015 - 2
//  B  - 25/10/2015 - 3
//  C  - 23/10/2015 - 3
//  C  - 24/10/2015- 0
//  C - 25/10/2015 -  3

所得输出:

23  3
24  3
25  1
23  1
24  2
25  3
23  3
25  3

正如您所看到的，分组是正确的，但是像整个Date和Alias这样的信息丢失了，并且我无法在嵌套循环的代码中检索它们。

有什么建议吗?如何获得所需的输出?

无法在按linq分组后保留属性

这里基本上有两个问题:

  • 你按Day而不是Date分组，我怀疑你想这么做
  • 你没有使用你已经在外部分组
    • 中将别名作为关键字的事实

实际上，您可以通过按别名和日期一次分组来更简单地做到这一点:

var query = usages.GroupBy(r => new { r.Alias, r.HitDate.Date },
                           (key, elements) => new { key.Alias,
                                                    key.Date,
                                                    Count = elements.Count() })
                  .OrderBy(x => x.Alias)
                  .ThenBy(x => x.Date);
foreach (var item in query)
{
    Console.WriteLine("{0} {1} {2}", item.Alias, item.Date, item.Count);
}

也可以在select语句中选择该值

var g = usages.GroupBy(r => r.Alias); 
foreach (var u in g) 
{ 
    var x = u.GroupBy(r => r.HitDate.Day)
             .Select(gr => new { 
                                   Alias=u.Alias,
                                   HitDate=gr.Key, 
                                   Count=gr.Count() 
             }); 
    foreach (var m in x) 
    {
        Console.WriteLine(m.HitDate + " " + m.Count); 
    } 
}
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