c# 短链接生成

 public static string GetShortUrl(string url)
         {
             //可以自定义生成MD5加密字符传前的混合KEY
             string key = DateTime.Now.ToString();
             //要使用生成URL的字符
             string[] chars = new string[]{
              "a","b","c","d","e","f","g","h",
              "i","j","k","l","m","n","o","p",
              "q","r","s","t","u","v","w","x",
              "y","z","","","","","","",
              "","","","","A","B","C","D",
              "E","F","G","H","I","J","K","L",
              "M","N","O","P","Q","R","S","T",
              "U","V","W","X","Y","Z"
               };

             //对传入网址进行MD5加密
             string hex = System.Web.Security.FormsAuthentication.HashPasswordForStoringInConfigFile(key + url, "md5");

             string[] resUrl = new string[];
             for (int i = ; i < ; i++)
             {
                 //把加密字符按照8位一组16进制与0x3FFFFFFF进行位与运算
                 int hexint = 0x3FFFFFFF & Convert.ToInt32("0x" + hex.Substring(i * , ), );
                 string outChars = string.Empty;
                 for (int j = ; j < ; j++)
                 {
                     //把得到的值与0x0000003D进行位与运算，取得字符数组chars索引
                     int index = 0x0000003D & hexint;
                     //把取得的字符相加
                     outChars += chars[index];
                     //每次循环按位右移5位
                     hexint = hexint >> ;
                 }
                 //把字符串存入对应索引的输出数组
                 resUrl[i] = outChars;
             }
             return resUrl[new Random().Next(, )];
         }