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        private string buildurl(string url,string param)
        {
            string url1=url;
            if(url.IndexOf(param)>0)
            {
                if(url.IndexOf("&",url.IndexOf(param)+param.Length)>0)
                {
                    url1=url.Substring(0,url.IndexOf(param)-1)+url.Substring(url.IndexOf("&",url.IndexOf(param)+param.Length)+1);
                }
                else
                {
                    url1=url.Substring(0,url.IndexOf(param)-1);
                }
                return url1;
            }
            else
            {
                return url1;
            }
        }

去除多个如下使用：buildurl(buildurl(buildurl(url,param1),param2),param3)))