在C＃中，如何按对象中的属性对集合进行排序？

Question

I have a collection of Person objects and a person can belong to many teams

public class Person
{
     public List<string> Teams();
} 

so I have a collection of these objects

List<Person> people = GetPeople();

Now given the collection I want to get the list of most used teams

I can get a full list of all teams by doing this:

   var teams = people.SelectMany(r=>r.Teams);

or I can get a distinct list of teams by doing this:

   var teams = people.SelectMany(r=>r.Teams).Distinct(new TeamComparer());

but I now want to get the top 10 teams.

What is the correct way to sort teams by the most used? So for example if I have

  var person = new Person(){Teams = new List<string>{"Team A", "Team D"} }
  var person2 = new Person(){Teams = new List<string>{"Team B", "Team C"} }
  var person3 = new Person(){Teams = new List<string>{"Team B", "Team C"} }
  var person4 = new Person(){Teams = new List<string>{"Team B", "Team D"} }

so in the example above, it would return in order:

Team B
Team C
Team D
Team A

Answer 1

If you want to get ten teams with the highest usage count, you should group them, rather than eliminating the duplicates using Distinct() . Once you have your groups, sort by group count, and take the first ten, like this:

var topTen = people
    .SelectMany(r => r.Teams)          // Get the teams with duplicates
    .GroupBy(t => t)                   // Group by team
    .OrderByDescending(g => g.Count()) // Sort by count
    .Take(10)                          // Take top ten
    .Select(g => g.Key)                // Drop groups
    .ToList();                         // Make a list

Answer 2

List<Person> lstpeople = GetPeople();
lstPerson = lstPerson.OrderBy(x => x.personID).toList();
lstPerson = lstPerson.orderbydescending(x => x.personID).toList();