Task异步方法调用出现重复值

问题:

public static void TransDutySync(IEnumerable<KeyValueEntity> _Positions, int servername)
        {

            foreach (var po in _Positions)
            {
               string json = "{\"id\":\"" + po.Key_Id + "\",\"name\":\"" + po.Value + "\",\"remark\":\"" + po.Comments + "\"}";       
         Thread.Sleep(30);
                HttpHelperSync.UpdatePositionSync(json, servername);//同步
                Task.Run(() => HttpHelperSync.UpdatePositionSync(json, servername));//异步
            }

        }



  public static string HttpPostSync(UrlCollection urlCollection)
        {


            string json = urlCollection.json;
            HttpWebRequest request = (HttpWebRequest)WebRequest.Create(urlCollection.Url);
            request.Method = "POST";
            request.ContentType = "application/json";           
            request.Headers.Add(HttpRequestHeader.Authorization,"Basic "+ urlCollection.Token);
            string retString = string.Empty;int StatusCode = 0;
            try
            {
                Stream myRequestStream = request.GetRequestStream();
                StreamWriter myStreamWriter = new StreamWriter(myRequestStream, Encoding.GetEncoding("utf-8"));
                myStreamWriter.Write(json);
                myStreamWriter.Close();
                HttpWebResponse response = request.GetResponse() as HttpWebResponse;
                StatusCode = (int)response.StatusCode;
                Stream myResponseStream = response.GetResponseStream();
                StreamReader myStreamReader = new StreamReader(myResponseStream, Encoding.GetEncoding("utf-8"));
                retString = myStreamReader.ReadToEnd();
                myStreamReader.Close();
                myResponseStream.Close();


            }
            catch (WebException ex)
            {
                retString = ex.Message;
                HttpWebResponse response = (HttpWebResponse)ex.Response;
                StatusCode = (int)response.StatusCode;
            }
           
            RECLOUD_DATASYNC_LOG _log = new RECLOUD_DATASYNC_LOG();
            _log.LOGTIME = DateTime.Now;
            _log.LOGTITLE = logTitle;
            _log.RESPONSECODE = StatusCode;
            _log.LOGCONTENT = json;
            _log.RESPONSECONTENT = retString;
            _log.SERVERNAME = urlCollection.ServerName;//这个值每个请求是一样的
            HttpHelper.WriteLog(_log);//写数据库日志


            return retString;
        }
 

 

 

请教一下，如果写成同步方法，是没有问题的，如果写成异步形式，358行更新，数据库中就出现50-70行值是重复的，这怎么改呢？

回答1:

本地变量引起的问题。
你的代码，没复制完整吧？在foreach过程中，json是不断的改变吧?
参考第一个示例：https://docs.microsoft.com/zh-cn/dotnet/api/system.threading.tasks.taskfactory.startnew

回答2:

应该这么写

var tasks = new List<Task>();
 foreach (var po in _Positions)
            {
                string json = "{}";
                Thread.Sleep(30);
                //HttpHelperSync.UpdatePositionSync(json, servername);//同步
                //Task.Run(() => HttpHelperSync.UpdatePositionSync(json, servername));//异步
               tasks.Add(Task.Run(() => HttpHelperSync.UpdatePositionSync(json, servername)));
            }
Task.WaitAll(task.ToArray());