Counting average on list<T> field

问题

I have list of A, and I want to count average on it's field a.
What's the best way to do it?

class A
{
    int a;
    int b;
}
void f()
{
    var L = new List<A>();
    for (int i=0; i<3; i++)
    {
        L.Add(new A(){a = i});
    }
}

回答1:

Enumerable.Average has an overload that takes a Func<T, int> as an argument.

using System.Linq;

list.Average(item => item.a);

回答2:

You could try this one:

var average = ListOfA.Select(x=>x.a).Average();

where ListOfA is a List of objects of type A.

回答3:

You can use Enumerable.Average

var average = L.Select(r => r.a).Average();

来源：https://stackoverflow.com/questions/24386928/counting-average-on-listt-field