GUID转换成16位字符串或19位数字并确保唯一

using System;  
using System.Collections.Generic;  
using System.Linq;  
using System.Text;  
using System.Threading.Tasks;  
  
namespace ConsoleApplication1  
{  
    class Program  
    {  
        static void Main(string[] args)  
        {  
            string str = GuidTo16String();  
            Console.WriteLine(str);  
            Console.WriteLine(str.Length);  
            Console.Read();  
        }  
        public static string GuidTo16String()  
        {  
            long i = 1;  
            foreach (byte b in Guid.NewGuid().ToByteArray())  
                i *= ((int)b + 1);  
            return string.Format("{0:x}", i - DateTime.Now.Ticks);  
        }  
  
        /// <summary>    
        /// 根据GUID获取19位的唯一数字序列    
        /// </summary>    
        /// <returns></returns>    
        public static long GuidToLongID()  
        {  
            byte[] buffer = Guid.NewGuid().ToByteArray();  
            return BitConverter.ToInt64(buffer, 0);  
        }   
    }  
}