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

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            string s = "12345";
            var query = from x in s
                        from y in s
                        where x != y
                        select s.Replace(x, '*').Replace(y, '*');
            foreach (var item in query)
                Console.WriteLine(item);
        }
    }
}

------解决方案--------------------
C# code
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            string s = "12345";
            var query = (from x in s
                        from y in s
                        where x != y
                        orderby x + y descending
                        select s.Replace(x, '*').Replace(y, '*')).Distinct();
            foreach (var item in query)
                Console.WriteLine(item);
        }
    }
}

------解决方案--------------------

探讨

这个能通用吗 可能有8选5 7选3 等等