Design Patterns 07 - 代理模式

abstract class Subject {
    public abstract void Request();
}

class RealSubject : Subject {
    public override void Request() {
        // todo
    }
}

class Proxy : Subject {
    RealSubject realSubject;
    public override void Request() {
        if(realSubject == null) {
            realSubject = new RealSubject();
        }
        realSubject.Request();
    }
}

public static void Main(string[] args) {
    Proxy proxy = new Proxy();
    proxy.Request();
}