在C＃中，如何按列表大小对列表进行排序后排序？

Question

Lets say I have a collection of car objects

3 blue cars
10 yellow car
5 red cars

List<Car> cars = GetList();
var groupBy = cars.GroupBy(r=>r.Color);

I now want to sort the groupBy grouped collection in descending order so I first get the yellow cars, then red and then blue when i loop through the list

What is the correct way to sort a grouped list by the size of the collection in that entry of the group by list?

Answer 1

var result = cars.GroupBy(r=>r.Color).OrderByDescending(g => g.Count());

Answer 2

When you group a collection, you will get a IEnumerable<Grouping<TKey, TValue>> collection which has the Key property and Value property. The Key is the value which you have grouped and the Value is the entire object grouped by the Key . You also have all extensions for IEnumerable .

In your case, you could just call the OrderByDescending method passing the Count() method from group colelction, for sample:

var result = cars.GroupBy(r=>r.Color).OrderByDescending(x => x.Count());