代理

using System;

//Client
var proxy = new ImageProxy("1.png");
//operation without creating a RealSubject
var fileName = proxy.GetFileName();
//forwarded to the RealSubject
proxy.Draw();

Console.WriteLine(fileName);

//Subject
abstract class Graphic {
    protected string FileName;

    public abstract void Draw();

    public string GetFileName() {
        return FileName;
    }
}

//RealSubject
class Image: Graphic {

    public Image(string fileName) {
        FileName = fileName;
    }

    //Request()
    public override void Draw() {
        Console.WriteLine("draw " + FileName);
    }
}

//Proxy
class ImageProxy: Graphic {
    Image _image;

    public ImageProxy(string fileName) {
        FileName = fileName;
    }

    public override void Draw() {
        GetImage().Draw();
    }

    private Image GetImage()
    {
        return _image ??= new Image(FileName);
    }
}