// Sample for String.Join(String, String[], int int)
using System;

class Sample {
    public static void Main() {
    String[] val = {"apple", "orange", "grape", "pear"};
    String sep   = ", ";
    String result;

    Console.WriteLine("sep = ‘{0}‘", sep);
    Console.WriteLine("val[] = {{‘{0}‘ ‘{1}‘ ‘{2}‘ ‘{3}‘}}", val[0], val[1], val[2], val[3]);
    result = String.Join(sep, val, 1, 2);
    Console.WriteLine("String.Join(sep, val, 1, 2) = ‘{0}‘", result);
    }
}
/*
This example produces the following results:
sep = ‘, ‘
val[] = {‘apple‘ ‘orange‘ ‘grape‘ ‘pear‘}
String.Join(sep, val, 1, 2) = ‘orange, grape‘
*/

Console.WriteLine("************************************************************");

        List<string> names = new List<string> { "李意义1", "李意义2", "李礼物1", "李礼物2", "单罗1", "单罗2", "单1", "单2", "单", "1", "2", "罗", "Yuri" };
        //目标状态：{李***，李***，李***，单**,单**,单*,单*,单,1,2,罗,Y***};
        string[] find = { "*", "*", "*", "*", "*", "*", "*", "*", "*", "*", "*", "*", "*", "*", "*", "*", "*", "*", "*", "*", "*", "*", "*", "*" };
        for (int i = 0; i < names.Count; i++)
        {
            string temp = names[i][0] + string.Join("", find, 0, names[i].Length-1);
            Console.WriteLine(temp);
        }

        List<string> phone = new List<string> { "152", "15347834899", "1", "8967382" };

        for (int i = 0; i < phone.Count; i++)
        {
            if (phone[i].Length>7)
            {
                string temp = phone[i].Substring(0, 3) + "****" + phone[i].Substring(7);
                Console.WriteLine(temp);    
            }
            else if (phone[i].Length>3)
            {
                string temp = phone[i].Substring(0, 3) +string.Join("",find,0, phone[i].Length-3);
                Console.WriteLine(temp);
            }
            else
            {
                Console.WriteLine(phone[i]);
            }
        }

        Console.ReadKey();