link中aggregate有什么用，和selectmany的区别是什么？

Question

link中aggregate有什么用，和selectmany的区别是什么？

Answer 1

我把concat也实现了，请看

 using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            int[][] arr = new int[][]
            {
                new int[] { 1, 2, 3 },
                new int[] { 4, 5 },
                new int[] { 6, 7 }
            };
            int[] query1 = arr.MySelectMany(x => x).ToArray();
            foreach (var item in query1)
                Console.WriteLine(item);
            Console.WriteLine();
            int[] query2 = arr.MyAggregate(new int[] { }, (pre, curr) => pre.MyConcat(curr));
            foreach (var item in query2)
                Console.WriteLine(item);
        }
    }

    static class MyLinq
    {
        public static int[] MyConcat(this int[] data1, int[] data2)
        { 
            int[] result = new int[data1.Length + data2.Length];
            for (int i = 0; i < data1.Length; i++)
            {
                result[i] = data1[i];
            }
            for (int i = data1.Length; i < data1.Length + data2.Length; i++)
            {
                result[i] = data2[i - data1.Length];
            }
            return result;
        }

        public static IEnumerable<int> MySelectMany(this int[][] data, Func<int[], IEnumerable<int>> selector)
        {
            foreach (int[] item in data)
                foreach (int i in selector(item))
                    yield return i;
        }

        public static int[] MyAggregate(this int[][] data, int[] seed, Func<int[], int[], int[]> func)
        {
            int[] result = seed;
            foreach (int[] item in data)
                result = func(result, item);
            return result;
        }
    }
}