Observer 观察者模式 （HeadFirst设计模式 c#）

Observer.cs
using System;
using System.Text;
using System.Collections.Generic;
namespace Observer
{
   
    public interface ISubject
    {
        void RegisterObserver(IOvserver o);
        void RemoveObserver(IOvserver o);
        void NotifyObserver();
    }
    public interface IOvserver
    {
        void update(float temp, float humidity, float pressure);
    }
    public interface IDisplayElement
    {
        void display();
    }
    public class WeatherData:ISubject
    {
        private List<IOvserver> obList;
        private float temperature;
        private float humidity;
        private float pressure;
        public WeatherData()
        {
            obList = new List<IOvserver>();
        }
        public void RegisterObserver(IOvserver o)
        {
            obList.Add(o);
        }
        public void RemoveObserver(IOvserver o)
        {
            if (obList.IndexOf(o) >= 0)
            {
   &nb