C# 生成随机字符串

以某个字符串中的随机字符组成一定长度下的随机字符串

using System;
using System.Collections.Generic;
using System.Linq;
using System.Security.Cryptography;
using System.Text;
using System.Threading.Tasks;
 
namespace ConsoleApp3
{
    class Program
    {        
        static void Main(string[] args)
        {
            string retStr1;
            string retStr2;
            retStr1 = GetRandomString1("Hello World", 20);   
            retStr2 = GetRandomString2("Hello World", 20);
            Console.WriteLine(retStr1);
            Console.WriteLine(retStr2);
            Console.ReadKey();
        }
 
        //以chars中的字符生成length长度的随机字符串
        //RNGCryptoServiceProvider为例
        public static string GetRandomString1(string chars, int length)
        {
            StringBuilder sb = new StringBuilder();
            RNGCryptoServiceProvider rnd = new RNGCryptoServiceProvider();
            byte[] ary = new byte[8];
            for (int index = 0; index < length; index++) //密码长度为循环次数
            {
                rnd.GetBytes(ary);
                sb.Append(chars[(int)Math.Round(Math.Abs(BitConverter.ToInt64(ary, 0)) / (decimal)long.MaxValue * (chars.Length - 1), 0)]);
            }
            return sb.ToString();
        }
 
        //以chars中的字符生成length长度的随机字符串
        //Random为例
        public static string GetRandomString2(string chars, int length)
        {
            int charIndex;
            Random rnd = new Random();
            StringBuilder sb = new StringBuilder();
            for (int index = 0; index < length; index++) //密码长度为循环次数
            {
                charIndex = rnd.Next(chars.Length);
                sb.Append(chars[charIndex]);
            }
            return sb.ToString();
        }
    }
}