生成随机不重复长度编码

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Security.Cryptography;
namespace WinFormsApp1
{
    public class CodeHelp
    {
        public static string GetUniqueKey(int maxSize = 8)
        {
            char[] chars = new char[62];
            string a = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890";
            chars = a.ToCharArray();
            RNGCryptoServiceProvider crypto = new RNGCryptoServiceProvider();
            int size = maxSize;
            byte[] data = new byte[size];
            crypto.GetNonZeroBytes(data);
            StringBuilder result = new StringBuilder(size);
            foreach (byte b in data)
            {
                result.Append(chars[b % (chars.Length - 1)]);
            }
            return result.ToString();
        }
    }
}