Taskstart date of an task in ExchangeWebService not changing while other fields are changing

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C#

WinRT

Hi All,

I am developing a window 8 metro app where i have to use the ExchaneWebServices to create tasks and display all tasks back into my app. Athough I have done it through webservice Now I have to make the task editable for which I am using the Task UniqueId to search the task and then edit it contents but I am facing a problem in this the Task all fields get updated except the Taskstart date any help why it is not changing will be highly appreciated.

This works fine when I edit the tasks through the office365.

My Code is Like this

public void GetTaskEdited(EWSTask EWSTaskObject, string TaskUniqueid)
        { 

		//Code to connect to the Exchange

            ExchangeService service;
            service = new ExchangeService(ExchangeVersion.Exchange2007_SP1);
            service.Credentials = new WebCredentials(Authentication.UserName, Authentication.Password);
            service.AutodiscoverUrl(Authentication.UserName, RedirectionUrlValidationCallback);

//Filter the task according to the TaskUniqueId

FindItemsResults<item> foundItems=service.FindItems(WellKnownFolderName.Tasks,
                 new SearchFilter.IsEqualTo(TaskSchema.Id, TaskUniqueid),
                 new ItemView(5));

              Item foundItem = foundItems.FirstOrDefault();
            if (foundItem != null && foundItem is Task)
            {
                Task foundTask = (Task)foundItem;

                foundTask.Subject = EWSTaskObject.Subject;
                foundTask.Body = EWSTaskObject.Body;
                foundTask.StartDate = EWSTaskObject.TaskStartDate;
                foundTask.IsReminderSet = EWSTaskObject.ReminderSet;
                foundTask.ReminderMinutesBeforeStart = EWSTaskObject.ReminderMinutes;
                foundTask.Importance = EWSTaskObject.TaskImportance;
                foundTask.Status = EWSTaskObject.TaskStatus;
                foundTask.DueDate = EWSTaskObject.TaskDueDate;
                foundTask.ReminderDueBy = EWSTaskObject.TaskDueDate.AddHours(2);
                DayOfTheWeek[] days = new DayOfTheWeek[EWSTaskObject.TaskRecurrenceDay.Count];
                for (int i = 0; i < EWSTaskObject.TaskRecurrenceDay.Count; i++)
                {
                    days[i] = EWSTaskObject.TaskRecurrenceDay[i];
                }
                if (EWSTaskObject.ReminderSet == true)
                {
                    foundTask.Recurrence = new Recurrence.WeeklyPattern(startDate: foundTask.StartDate.Value, interval: 1, daysOfTheWeek: days);
                }

               // foundTask.Save();                
                foundTask.Update(ConflictResolutionMode.AutoResolve);

            }

        }

The entire fields are updated except the task startdate