Task Asnyc 异常问题

/// <summary>
        /// async 异常捕获问题
        /// </summary>
        /// <param name="context"></param>
        /// <returns></returns>
        static async Task<string> TestException(string context) {
            return string.Format("【{0}】 长度:【{1}】",context,context.Length);
        }

        /// <summary>
        /// 该方法无法获取异常
        /// </summary>
        static void Test1()
        {
            try
            {
                 //产生异常  无法捕获异常
                 TestException(null).ContinueWith(r =>{
                     Console.WriteLine(r.Result);
                 });
            }
            catch (Exception ex)
            {
                throw;
            }
        }

        /// <summary>
        /// 不能报异常（async与await一起使用）
        /// </summary>
        /// <returns></returns>
        static async Task Test2()
        {
            string result = await TestException(null);
            string test = result;
        }

 Http async / await 方式请求实例：

    public static async Task<string> HttpGet(string Url)
        {
            HttpWebRequest request = (HttpWebRequest)WebRequest.Create(Url);
            request.Method = "GET";
            request.ContentType = "text/html;charset=UTF-8";

            using (var response =await request.GetResponseAsync())
            {
                Stream myResponseStream = response.GetResponseStream();
                StreamReader myStreamReader = new StreamReader(myResponseStream, Encoding.UTF8);
                string retString = myStreamReader.ReadToEnd();
                return retString;
            }
        }

        public static async Task<string> HttpPostAsync(string url, string postData)
        {
            try
            {
                byte[] byteArray = Encoding.UTF8.GetBytes(postData);
                HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
                request.Method = "POST";
                request.ContentType = "application/json";
                request.ContentLength = byteArray.Length;
                using (Stream myRequestStream = await request.GetRequestStreamAsync())
                {
                    myRequestStream.Write(byteArray, 0, byteArray.Length);
                    WebResponse response = request.GetResponse();
                    StreamReader myStreamReader = new StreamReader(response.GetResponseStream(), Encoding.GetEncoding("utf-8"));
                    return myStreamReader.ReadToEnd();
                }
            }
            catch (Exception ex)
            {
                Logger.Info(ex);
                return string.Empty;
            }
           
        }
        
        public static async Task<string> HttpPostAsync(string url, Dictionary<string,string> paramList)
        {
            try
            {
                HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
                StringBuilder sb = new StringBuilder();
                foreach (var item in paramList)
                {
                    sb.Append(item.Key + "=" + item.Value + "&");
                }
                string paramData = sb.ToString().Trim('&');
                byte[] data = System.Text.Encoding.UTF8.GetBytes(paramData);
                request.Method = "post";
                //这句不能少  不难post请求 得不到对应的响应结果
                request.ContentType = "application/x-www-form-urlencoded";
                using (Stream myRequestStream = await request.GetRequestStreamAsync())
                {
                    myRequestStream.Write(data, 0, data.Length);
                    WebResponse response = request.GetResponse();
                    StreamReader myStreamReader = new StreamReader(response.GetResponseStream(), Encoding.GetEncoding("utf-8"));
                    return myStreamReader.ReadToEnd();
                }
            }
            catch (Exception ex)
            {
                Logger.Info(ex);
                return string.Empty;
            }

        }

    /// <summary>
        /// PPTV点卡充值
        /// </summary>
        /// <param name="mobie">手机号</param>
        /// <param name="cardnumber">点卡卡密</param>
        /// <returns></returns>
        public async Task<string> ExchangePPTVCard(string mobie, string cardnumber)
        {
            string agent = "lemon_act";
            string agentkey = "HF0abDEc";
            string username = mobie;
            //aesyhhxw72453525  月卡
            //hnscpyau66772763  半年卡
            //mwusrbdu45743377  年卡
            //string cardnumber = "hnscpyau66772763";
            string urlEncodeUsername = StringHelper.UrlEncode(username);
            string sign = StringHelper.MD5(StringHelper.UrlEncode(string.Format("{0}&{1}&{2}",username,cardnumber,agentkey)));
            Dictionary<string, string> paramList = new Dictionary<string, string>();
            paramList.Add("username", urlEncodeUsername);
            paramList.Add("cardnumber", cardnumber);
            paramList.Add("agent", agent);
            paramList.Add("sign", sign);
            string url = "https://api.vip.pptv.com/ppcard/exchange";
            string result = await HttpHelper.HttpPostAsync(url, paramList);
            UserPPTVCardExchangeResultModel exchangeResult = JsonConvert.DeserializeObject<UserPPTVCardExchangeResultModel>(result);
            return result;
        }

/// <summary>
        /// 充值点卡
        /// </summary>
        /// <param name="mobile">手机号(手机号必须注册)</param>
        /// <param name="cardnumber">点卡卡密</param>
        /// <returns></returns>
         [HttpGet, Route("ExchangeCard")]
        public async Task<Result<bool>> ExchangeCard(string mobile,string cardnumber)
        {
            Result<bool> result = new Result<bool>();
            try
            {
                string secretKey = Request.Headers.GetValues("SecretKey").FirstOrDefault();
                ChannelsService channelservice = new ChannelsService();
                int channelId = channelservice.GetChannerIdBySecretKey(secretKey);

                UsersService userService = new UsersService();
                //1.判断手机是否存在
                bool isExist = userService.IsRegisterPPTVByMobile(mobile, channelId);
                result.ReturnCode = StateCode.Success;
                if (!isExist)
                {
                    Logger.Warn(string.Format("【0】手机号尚未注册",mobile));
                    result.Data = false;
                    result.ReturnMsg = "该手机尚未注册";
                    return result;
                }
                //2.判断该点卡是否可以使用
                bool isEnable = await PPTVCardInfo(mobile,cardnumber);
                if (!isEnable)
                {
                    Logger.Warn(string.Format("【0】点卡卡密已经被使用", cardnumber));
                    result.Data = false;
                    result.ReturnMsg = "该点卡卡密已经被使用";
                    return result;
                }
                //3.充值PPTV点卡
                bool isChange = await ExchangePPTVCard(mobile, cardnumber);
                if (!isChange)
                {
                    result.Data = false;
                    result.ReturnMsg = "该点卡卡密已经被使用";
                    return result;
                }
                result.Data = userService.ExchangePPTVCard(cardnumber);
                if (result.Data)
                {
                    result.ReturnMsg = "充值点卡成功";
                }
                else
                {
                    result.ReturnMsg = "充值点卡失败";
                }
            }
            catch (Exception ex)
            {
                result.ReturnMsg = "服务器内部发生异常";
                Logger.Error("UsersController[ExchangeCard]", ex);
            }
            return result;
        }

 使用Task.Run(()=>{})方式执行

 /// <summary>
            /// 更新订单状态
            /// </summary>
            /// <param name="consumptionId">订单ID</param>
            /// <param name="totalFee">总费用</param>
            /// <param name="status">状态</param>
            /// <returns></returns>
            public async Task<bool> CheckUserConsumptionStatus(Guid consumptionId, string buyerEmail, decimal totalFee, int status)
            {

                return await Task.Run(() => {
                    //TODO
                     return true;
   
                });
                
            }