This describes usage of delegates in C#

readme.md

Blur filter decalres two methods: -ApplyGaussFilter -ApplyBlur

These methods have following signature: Params => Image, Returns => Image

The FileHandeler class invokes ImageProcessor in which is declared FilterHandler (which is a delegate), to which is attached other methods with same signatures.

Once functions are attached to the delegate - "StartProcessing" method (from ImageProcessor class) is called which runs all the filters attached to the delegate.

blur-filter.cs

using Data.Model;
using System;
using System.Threading;

namespace image.processor 
{
    class BlurFilter 
    {
        public static Image ApplyBlur (Image img) 
        {
            Console.WriteLine("Applying blur....");
            Console.WriteLine("Will be waiting for 3 sec");
            Thread.Sleep(3000);
            img.IsBlurred = true;
            return img;
        }

        public static Image ApplyGaussFilter (Image img) 
        {
            Console.WriteLine("Applying Gausssian filtering....");
            Console.WriteLine("Will be waiting for 5 sec");
            Thread.Sleep(5000);
            img.IsBlurred = true;
            return img;
        }
    }

    class ImageProcessor 
    {
        public delegate Image FilterHandler(Image img);

        public Image StartProcessing(Image img, FilterHandler filter) 
        {
            var result = filter(img);
            return result;
        }
    }
}

file-handeler.service.cs

using Data.Model;
using image.processor;

namespace fileHandeler 
{

    class FileHandeler 
    {
        public static void GetAndProcessImage() 
        {
            var img = TransferImage();
            var imageProcessor = new ImageProcessor();
            ImageProcessor.FilterHandler filterHandler = BlurFilter.ApplyBlur;
            filterHandler += BlurFilter.ApplyGaussFilter;
            imageProcessor.StartProcessing(img, filterHandler);
        }

        public static Image TransferImage() 
        {
            var image = new Image();
            return image;
        }
    }

}

Image.cs

namespace Data.Model 
{
    class Image 
    {
        public string Title { get; set; }

        public bool IsBlurred { get; set; } = false;
    }
}

program.cs

using System;
using fileHandeler;

namespace test1
{
    class Program
    {
        static void Main(string[] args)
        {
            FileHandeler.GetAndProcessImage();
            Console.WriteLine("Press any key to exit....");
            Console.ReadKey();
        }
    }
}