谁能帮忙吧这个方法改下，把LinQ改成平常的
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApplication1
{
class Program
{
static void Main(string[] args)
{
foreach (var item in foo(new List<Char>() { 'a', 'b' }, 6))
Console.WriteLine(item);
}

static IEnumerable<string> foo(List<char> metachars, int length)
{
if (length == 1) return metachars.Select(x => x.ToString());
return metachars.SelectMany(x => foo(metachars, length - 1).Select(y => y + x));
}
}
}



把上面的方法不用Linq，就平常的 递归调
谢谢 了
[解决办法]
更准确的说，那是Lamda
[解决办法]

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

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            foreach (var item in foo(new List<Char>() { 'a', 'b', 'c' }, 4))
                Console.WriteLine(item);
        }

        static IEnumerable<string> foo(List<char> metachars, int length)
        {
            if (length == 1)
                foreach (char x in metachars)
                    yield return x.ToString();
            else
                foreach (char y in metachars)
                    foreach (string x in foo(metachars, length - 1))
                        yield return y + x;
        }
    }
}

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