Linq：按月分组总计

Question

我有一个简单的业务对象：

Crime 
     Date
     PersonsInvolved

我需要一个每月总人数列表。这些数据是1年，所以不需要考虑这一年。

Jan 5
Feb 3
Mar 5

等等

如果我有这样的内存集合，如何在Linq中完成：

List<Crime>() crimes;

Answer 1

crimes.GroupBy(c => c.Date.Month)
      .Select(g => new { Month = g.Key, Count = g.Count() });

Answer 2

var q =  from i in crimes
    group i by i.Date.ToString("MMM") into grp
    select new {Month = grp.Key, Count = grp.Sum(i => i.Persons)};

Answer 3

List<Crime>() crimes = ...
var crimesPerMonth = crimes.GroupBy(x => x.Date.Month);