/// <summary>
 /// ɾ������
 /// </summary>
 /// <param name="task"></param>
 /// <returns></returns>
 public bool DeleteTask(ITask task)
 {
     bool b = taskList.Delete(task);
     if(b)
     {
         task.StopTask();
         return true;
     }
     else
     {
         return false;
     }
 }