C# 之HTTP请求get,post带重试参数

public class WebHttp
    {
        /// <summary>
        /// get请求带重试
        /// </summary>
        /// <param name="Url"></param>
        /// <param name="postDataStr"></param>
        /// <param name="sum"></param>
        /// <returns></returns>
        public static string HttpGet(string Url, string postDataStr, int sum)
        {
            string temp=null;
            for (int i = ; i < sum; i++)
            {
                if (string.IsNullOrEmpty(temp) || string.IsNullOrEmpty(temp.Trim()))
                {
                    temp = HttpGet(Url, postDataStr);
                }
                else {
                    break;
                }
            }
            return temp;
        }
        /// <summary>
        /// post请求带重试
        /// </summary>
        /// <param name="Url"></param>
        /// <param name="postDataStr"></param>
        /// <param name="sum"></param>
        /// <returns></returns>
        public static string HttpPost(string Url, string postDataStr, int sum)
        {
            string temp = null;
            for (int i = ; i < sum; i++)
            {
                if (string.IsNullOrEmpty(temp) || string.IsNullOrEmpty(temp.Trim()))
                {
                    temp = HttpPost(Url, postDataStr);
                }
                else
                {
                    break;
                }
            }
            return temp;
        }
        /// <summary>
        /// GET请求与获取结果
        /// </summary>
        public static string HttpGet(string Url, string postDataStr)
        {
            try
            {
                HttpWebRequest request = (HttpWebRequest)WebRequest.Create(Url + (postDataStr == "" ? "" : "?") + postDataStr);
                request.Method = "GET";
                request.ContentType = "text/html;charset=UTF-8";
                request.Timeout = ;
                HttpWebResponse response = (HttpWebResponse)request.GetResponse();
                Stream myResponseStream = response.GetResponseStream();
                StreamReader myStreamReader = new StreamReader(myResponseStream, Encoding.UTF8);
                string retString = myStreamReader.ReadToEnd();
                myStreamReader.Close();
                myResponseStream.Close();
                return retString;
            }
            catch (Exception ex)
            {
                return null;
            }
        }
        /// <summary>
        /// POST请求与获取结果
        /// </summary>
        public static string HttpPost(string Url, string postDataStr)
        {
            try
            {
                HttpWebRequest request = (HttpWebRequest)WebRequest.Create(Url);
                request.Method = "POST";
                request.Timeout = ;
                request.ContentType = "application/x-www-form-urlencoded";
                request.ContentLength = postDataStr.Length;
                StreamWriter writer = new StreamWriter(request.GetRequestStream(), Encoding.ASCII);
                writer.Write(postDataStr);
                writer.Flush();
                HttpWebResponse response = (HttpWebResponse)request.GetResponse();
                string encoding = response.ContentEncoding;
                if (encoding == null || encoding.Length < )
                {
                    encoding = "UTF-8"; //默认编码
                }
                StreamReader reader = new StreamReader(response.GetResponseStream(), Encoding.GetEncoding(encoding));
                string retString = reader.ReadToEnd();
                return retString;
            }
            catch (Exception ex)
            {
                return null;
            }
        }
    }