URL中文参数乱码的一个解决办法

  string input = GetUrlParam(key).ToLower();//GetUrlParam 获取url参数原始编码的方法
            if (input.Length == 0)
                return string.Empty;

            //首先用utf-8进行解码 
            string result = HttpUtility.UrlDecode(input, Encoding.UTF8);

            // 将已经解码的字符再次进行编码.             
            string encode = HttpUtility.UrlEncode(result, Encoding.UTF8).ToLower();

            //与原来编码进行对比，如果不一致说明解码未正确，用gb2312进行解码 
            if (input != encode)
                result = HttpUtility.UrlDecode(input, Encoding.GetEncoding("gb2312"));

            return result;