public void AddWorkTime(WorkTime newWorkTime)
{
workTimes.Add(newWorkTime);
totalWorkTime = TimeSpan.Parse(totalWorkTime).Add(TimeSpan.Parse(newWorkTime.workTime)).ToString();
if (parentTask != null)
{
parentTask.totalWorkTime = TimeSpan.Parse(parentTask.totalWorkTime).Add(newWorkTime.CalculateWorkTime()).ToString();
}
}