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c# - 使用 linq 和 c# 的最大父 ID 的子节点数

问题描述

有什么方法可以获取具有最大父 ID 的孩子的数量并使用 linq 列出结果？
我正在尝试通过 Status 来获取值的总和，但我只能从孩子那里得到
我到目前为止所做的最后一个：

using System;
using System.Collections.Generic;
using System.Linq;

public class Program
{
    public static void Main()
    {
        
            var lstRfq = new List<RfqEvents>()
            {
                new RfqEvents(1,1,DateTime.Parse("2021-05-06 03:00:00+00"),1),
                new RfqEvents(2,2,DateTime.Parse("2021-05-06 03:00:00+00"),1),
                new RfqEvents(3,2,DateTime.Parse("2021-05-06 03:00:00+00"),1),
                new RfqEvents(4,3,DateTime.Parse("2021-05-06 00:00:00+00"),2),
                new RfqEvents(5,4,DateTime.Parse("2021-05-06 00:00:00+00"),2),
                new RfqEvents(6,5,DateTime.Parse("2021-05-06 00:00:00+00"),2),
                new RfqEvents(7,5,DateTime.Parse("2021-05-06 00:00:00+00"),2),
                new RfqEvents(8,5,DateTime.Parse("2021-05-06 00:00:00+00"),3),
                new RfqEvents(9,6,DateTime.Parse("2021-05-06 00:00:00+00"),3),
                new RfqEvents(10,6,DateTime.Parse("2021-05-06 00:00:00+00"),3),
            };

            var subquery = from c in lstRfq
                           group c by c.RfqId into g
                           select new InternalStatusInformations
                           {
                               RfqId = g.Key,
                               RfqEventId = g.Max(a => a.Id),
                               StatusId = g.Select(p => p.Status).FirstOrDefault()
                               
                           };
            var sss = from d in lstRfq.Where(p=> subquery.Select(p=>p.RfqEventId).Contains(p.Id))
                      group d by d.Status into z
                      select new InternalStatusInformations
                      {
                          StatusId = z.Key,
                          Total = z.Count(),
                          Past = z.Where(p => p.DueDate.HasValue && p.DueDate.Value.Date < DateTime.Now.Date).Count(),
                          Future = z.Where(p => p.DueDate.HasValue && p.DueDate.Value.Date > DateTime.Now.Date).Count(),
                          Today = z.Where(p => p.DueDate.HasValue && p.DueDate.Value.Date == DateTime.Now.Date).Count(),
                          FiveDays = z.Where(p => (p.DueDate.HasValue && p.DueDate.Value.Date > DateTime.Now.Date) && p.DueDate.HasValue && p.DueDate.Value.Date < DateTime.Now.Date.AddDays(5)).Count(),
                      };

            //expected: Status 1: 2 values
            //          Status 2: 3 values
            //          Status 3: 2 value

            //output:   Status 1: 2 values
            //          Status 2: 2 values
            //          Status 3: 2 values
        
        sss.Dump();
    }
            public class InternalStatusInformations
        {

            public int RfqEventId { get; set; }
            public int RfqId { get; set; }
            public int StatusId { get; set; }
            public int Future { get; set; }
            public int Past { get; set; }
            public int Today { get; set; }
            public int FiveDays { get; set; }
            public int Total { get; set; }
            public DateTime? DueDate { get; set; }

        }

        public class RfqEvents
        {
            public RfqEvents(int id, int rfqId, DateTime? dueDate, int status)
            {
                Id = id;
                RfqId = rfqId;
                DueDate = dueDate;
                Status = status;
            }
            public int Id { get; set; }
            public DateTime? DueDate { get; set; }
            public int RfqId { get; set; }
            public int Status { get; set; }
        }

}

https://dotnetfiddle.net/YoRsIG

但是结果有些不对劲，你们能帮帮我吗？

标签： c#linqgroup-by

解决方案

如果您只想计算RfqId每个状态中不同值的数量，应该这样做：

var pairs = lstRfq
    .GroupBy(evt => evt.Status)
    .Select(grouping =>
        {
            var status = grouping.Key;
            var count = grouping
                .Select(evt => evt.RfqId)
                .Distinct()
                .Count();
            return (status, count);
        });
foreach ((var status, var count) in pairs)
{
    Console.WriteLine($"Status {status}: {count} values");
}

输出是：

Status 1: 2 values
Status 2: 3 values
Status 3: 2 values

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