C# 什么'；使用或不使用委托的区别是什么

我对理解使用委托的概念有些怀疑，下面是我的委托示例

本例使用照片过滤软件作为实例，它将向照片添加过滤器，使用委托将增加将来添加新过滤器的灵活性

使用委托前

Photo.cs：

 class Photo
    {
        private string path;

        public Photo(string path)
        {
            this.path = path;
            Console.WriteLine("{0} imported", path);
        }

        public void Save()
        {
            Console.WriteLine("{0} photo saved", this.path);
        }
    }

PhotoFilter.cs：

class PhotoFilter
{
    public void AddBrigtness(Photo photo)
    {
        Console.WriteLine("Added Brightness");
    }

    public void AddFilter(Photo photo)
    {
        Console.WriteLine("Added Filter");
    }

    public void AddShadow(Photo photo)
    {
        Console.WriteLine("Added Shadow");
    }
}

PhotoProcesser.cs：

class PhotoProcesser
{
   public void Process(string path)
    {
        var photo = new Photo(path);
        var filter = new PhotoFilter();

        filter.AddBrigtness(photo);
        filter.AddFilter(photo);
        filter.AddShadow(photo);

        photo.Save();
    }
}

 delegate void PhotoMethodHandler(Photo p); // Delegate

    class PhotoProcesser
    {
       public void Process(string path,PhotoMethodHandler methodHandler)
        {
            var photo = new Photo(path);

            methodHandler(photo);

            photo.Save();
        }
    }

Program.cs：

class Program
{
    static void Main(string[] args)
    {
        var process = new PhotoProcesser();
        process.Process("123.jpg");
    }
}

  class Program
    {
        static void Main(string[] args)
        {
            var filter = new PhotoFilter();

            PhotoMethodHandler p = filter.AddBrigtness;
            p += filter.AddFilter;
            p += RemoveRedEyeFilter; // To simulate the flexibility of using Delegate

            var process = new PhotoProcesser();
            process.Process("123.jpg",p);
        }

        static void RemoveRedEyeFilter(Photo photo) // Newly added filter
        {
            Console.WriteLine("Added RemoveRedEye");
        }
    }

  class Program
    {    
        static void Main(string[] args)
        {
            var photo = new Photo("p1.jpg");
            var filter = new PhotoFilter();

            filter.AddBrigtness(photo);
            filter.AddFilter(photo);
            RemoveRedEyeFilter(photo);

            photo.Save();

        }

        static void RemoveRedEyeFilter(Photo photo) // Newly added filter
        {
            Console.WriteLine("Added RemoveRedEye");
        }
    } 

使用委托后

***Photo.cs和PhotoFilter.cs保持不变

PhotoProcesser.cs：

class PhotoProcesser
{
   public void Process(string path)
    {
        var photo = new Photo(path);
        var filter = new PhotoFilter();

        filter.AddBrigtness(photo);
        filter.AddFilter(photo);
        filter.AddShadow(photo);

        photo.Save();
    }
}

 delegate void PhotoMethodHandler(Photo p); // Delegate

    class PhotoProcesser
    {
       public void Process(string path,PhotoMethodHandler methodHandler)
        {
            var photo = new Photo(path);

            methodHandler(photo);

            photo.Save();
        }
    }

Program.cs：

class Program
{
    static void Main(string[] args)
    {
        var process = new PhotoProcesser();
        process.Process("123.jpg");
    }
}

  class Program
    {
        static void Main(string[] args)
        {
            var filter = new PhotoFilter();

            PhotoMethodHandler p = filter.AddBrigtness;
            p += filter.AddFilter;
            p += RemoveRedEyeFilter; // To simulate the flexibility of using Delegate

            var process = new PhotoProcesser();
            process.Process("123.jpg",p);
        }

        static void RemoveRedEyeFilter(Photo photo) // Newly added filter
        {
            Console.WriteLine("Added RemoveRedEye");
        }
    }

  class Program
    {    
        static void Main(string[] args)
        {
            var photo = new Photo("p1.jpg");
            var filter = new PhotoFilter();

            filter.AddBrigtness(photo);
            filter.AddFilter(photo);
            RemoveRedEyeFilter(photo);

            photo.Save();

        }

        static void RemoveRedEyeFilter(Photo photo) // Newly added filter
        {
            Console.WriteLine("Added RemoveRedEye");
        }
    } 

输出：

此时，我可以理解将委托用作函数指针的灵活性， 但是如果我们用另一种方式思考，如果我们不使用PhotoProcesser.cs并按以下方式更改Program.cs，我们也可以得到相同的结果：

Program.cs：

class Program
{
    static void Main(string[] args)
    {
        var process = new PhotoProcesser();
        process.Process("123.jpg");
    }
}

  class Program
    {
        static void Main(string[] args)
        {
            var filter = new PhotoFilter();

            PhotoMethodHandler p = filter.AddBrigtness;
            p += filter.AddFilter;
            p += RemoveRedEyeFilter; // To simulate the flexibility of using Delegate

            var process = new PhotoProcesser();
            process.Process("123.jpg",p);
        }

        static void RemoveRedEyeFilter(Photo photo) // Newly added filter
        {
            Console.WriteLine("Added RemoveRedEye");
        }
    }

  class Program
    {    
        static void Main(string[] args)
        {
            var photo = new Photo("p1.jpg");
            var filter = new PhotoFilter();

            filter.AddBrigtness(photo);
            filter.AddFilter(photo);
            RemoveRedEyeFilter(photo);

            photo.Save();

        }

        static void RemoveRedEyeFilter(Photo photo) // Newly added filter
        {
            Console.WriteLine("Added RemoveRedEye");
        }
    } 

输出：

它将获得与使用委托相同的结果和灵活性（在本例中添加新过滤器）

根据上面的例子，谁能给我一些指导，让我了解使用委派的好处/不同之处？谢谢

委托背后的思想（以及使用lambda或任何指向函数的指针）是能够将静态行为（由代码定义）转换为动态行为（由数据定义）

例如，我可以做：

Photo p = new Photo();
p = ApplyX(p);
p = ApplyY(p);
...

但有了代理，我可以做到

List<Func<Photo,Photo>> filters = Whatever();
Photo p = new Photo();
foreach(var filter in filters)
{
   p = filter(p);
}

List filters=Whatever（）；
照片p=新照片（）；
foreach（过滤器中的var过滤器）
{
p=过滤器（p）；
}

这将允许您在运行时更改过滤器列表（通过在过滤器列表中插入和删除委托）

---

您可以检查以下内容以进一步阅读：

这可能会对您有所帮助：EventHandler是委托的子级，因此情况有所不同。根据这个例子，我很困惑何时以及为什么我应该使用委托？在可重用性方面，如果我们需要多次处理相同的操作，使用委托可以减少一些代码。我说得对吗？