如何在任意层次结构中查找最具体的类型

Question

Let's say we have a collection of types:

var types = new[]
{
    typeof(IEnumerable<int>),
    typeof(ICollection<int>),
    typeof(Stack<int>),
    typeof(IList<int>),
    typeof(int[])
};

If you think about type hierarchy, you can imagine that:

                     IEnumerable<int>
                           |
                     ICollection<int>
                       /       \
              Stack<int>      IList<int>
                                  \
                                int[]

This isn't my actual problem, but it gets down to the following question:

Given a collection of types that all represent some tree (with a single root), how can I get a subcollection that contains those types that were leaves in the original collection.

So, for the collection above, the leaves would be Stack<int> and int[] .

How to do that in an elegant way? Any help will be greatly appreciated!

Edit

In my problem, I am dealing with actual types that derive from each other, creating a tree. For example, I can have:

class Root {}
class LeftChild : Root {}
class RightChild : Root {}
class LeftChildChild : LeftChild {}

In which case I would like to yield LeftChildChild and RightChild .

Answer 1

It seems to me that Type.IsAssignableFrom is your friend here. You want types that aren't assignable from any of the other types in the set:

using System;
using System.Collections.Generic;
using System.Linq;

class Program
{
    static void Main(string[] args)
    {
        var types = new[]
        {
            typeof(IEnumerable<int>),
            typeof(ICollection<int>),
            typeof(Stack<int>),
            typeof(IList<int>),
            typeof(int[])
        };

        var leaves = types.Where(candidate =>
            !types.Any(t => t != candidate && candidate.IsAssignableFrom(t)));
        Console.WriteLine(string.Join(Environment.NewLine, leaves));
    }
}