Question

我有一个包含以下数据的列表：

From        To      Gender    departure date
Delhi      Mumbai    M         16-Feb-18
Delhi      Mumbai    M         16-Feb-18
Delhi      Mumbai    F         16-Feb-18
Delhi      Mumbai    C         16-Feb-18
Mumbai     Mohili    F         16-Feb-18
Mumbai     Mohili    M         16-Feb-18
Mumbai     Mohili    C         16-Feb-18

我想根据From和To列对此列表进行分组，并通过LINQ计算每组中有多少男性，女性和儿童。我怎样才能做到这一点。我把它分组，但现在如何计算男性和女性的数量。

var list = result.Journey.GroupBy(x => new { x.From, x.To });

Answer 1

尝试以下代码，

        var list = travelars.GroupBy(x => new { x.From, x.To }).ToList().Select(e => new { 
            MaleCount = e.Count(g => g.Gender == "M"),
            FemaleCount = e.Count(g => g.Gender == "F"),
            ChildCount = e.Count(g => g.Gender == "C"),
        });

Answer 2

要知道的重要事项是GroupBy的返回类型是IGrouping<TKey, TElement>。此分组是可枚举的，并在枚举时生成元素。因此，分组可能是任何其他可枚举的LINQ查询。

var query = result.Journey
  .GroupBy(x => new { x.From, x.To })
  .Select(g => new
  {
    From = g.Key.From,
    To = g.Key.To,
    MCount = g.Count(x => x.Gender == "M"),
    FCount = g.Count(x => x.Gender == "F"),
    CCount = g.Count(x => x.Gender == "C")
  });

Answer 3

您似乎不明白GroupBy返回的内容。它返回一堆分组。每个IGrouping<T, U>本身就是该组中IEnumerable<U>个事物。

我建议你做的是按性别分组再次分组！这样，即使已将新的性别添加到模型中，您也不必添加代码来计算新的性别。

// using the new C# 7 tuple syntax!
foreach(var group in Journeys.GroupBy(x => (x.To, x.From))) {
    Console.WriteLine($"People traveling from {group.Key.Item1} to {group.Key.Item2}:");
    foreach (var subgroup in group.GroupBy(x => x.Gender)) {
        Console.WriteLine($"{subgroup.Key}: {subgroup.Count()} people");
    }
}

Answer 4

你可以试试这个，

  List<Journey> list = new List<Journey>();

            list.Add(new Journey() {From="Delhi",To="Mumbai",Gender=Gender.MALE });
            list.Add(new Journey() { From = "Delhi", To = "Mumbai", Gender = Gender.MALE });
            list.Add(new Journey() { From = "Delhi", To = "Mumbai", Gender = Gender.FEMALE });
            list.Add(new Journey() { From = "Delhi", To = "Mumbai", Gender = Gender.CHILD });
            list.Add(new Journey() { From = "Delhi", To = "Mumbai", Gender = Gender.MALE });
            list.Add(new Journey() { From = "Delhi", To = "Mumbai", Gender = Gender.MALE });
            list.Add(new Journey() { From = "Mumbai", To = "Mohili", Gender = Gender.FEMALE });
            list.Add(new Journey() { From = "Mumbai", To = "Mohili", Gender = Gender.CHILD });
            list.Add(new Journey() { From = "Mumbai", To = "Mohili", Gender = Gender.CHILD });

            var grp = list.GroupBy(s => new { s.From, s.To }).ToDictionary(d => d.Key, d => d.Select(i=>new JourneyCalc { From=i.From,To=i.To,Gender=i.Gender}).ToList());

            foreach (var item in grp)
            {
                var str = from val in item.Value group val by val.Gender into itmgrp select new JourneyCalc { Gender = itmgrp.Key, JourneyCount = itmgrp.Count() };
                foreach (JourneyCalc jc in str)
                {
                    Console.WriteLine(value: $"{item.Value[0].From} - {item.Value[0].To} => {jc.Gender} - {jc.JourneyCount}");
                }
            } 



    public class JourneyCalc
    {
        public string From { get; set; }
        public string To { get; set; }
        public Gender Gender { get; set; }
        public int JourneyCount { get; set; }
    }
    public enum Gender
    {        
        MALE,
        FEMALE,
        CHILD
    }
    public class Journey
    {
        public string From { get; set; }
        public string To { get; set; }
        public Gender Gender { get; set; }

    }

Output:

Delhi - Mumbai => MALE - 4
Delhi - Mumbai => FEMALE - 1
Delhi - Mumbai => CHILD - 1
Mumbai - Mohili => FEMALE - 1
Mumbai - Mohili => CHILD - 2

如何使用where子句使用LINQ组

4 个答案: