public static void Task(int taskID) { if (userList == null) { userList = new List <TaskModel>(); } TaskModel tm = taskList.Find(x => x.Id == taskID); TaskModel tm1 = userList.Find(x => x.Id == taskID); tm.accept = Task_State.Renounce; tm.finish = Task_State.Unfinished; if (tm1 == null) { UserTask.Add(tm); } SaveTask(); }