//Now this piece of code has a problem (it's not extensible)
//If you provide a framework for processing photos, and suppose a developer using this framework wants to apply a new filter
//Then you've to create that filter, and recompile and redeploy your code
//So this problem can be solved with delegates to make this framework extensible
public void Process(string path)
{
var photo = Photo.Load(path);
var filters = new PhotoFilters();
filters.ApplyBrightness(photo);
filters.ApplyContrast(photo);
filters.Resize(photo);
photo.Save();
}
public void Call()
{
//Without delegates (hence not extensible if we want to apply our own filter as we'll need to change PhotoProcessor class)
var photoProcessor = new PhotoProcessor();
photoProcessor.Process("photo.jpg");
//With custom delegates
var filters = new PhotoFilters();
PhotoProcessor.PhotoFilterHandler filterHandler = filters.ApplyBrightness; //Creating an instance of delegate and pointing it to a method having same signature
filterHandler += filters.ApplyContrast; //As our delegate here is pointing to multiple functions, so this is a multicaste delegate
filterHandler += RemoveRedEyeFilter;
photoProcessor.Process("photo.jpg", filterHandler);
//With .NET delegates
Action<Photo> actionFilterHandler = filters.ApplyBrightness;
actionFilterHandler += filters.ApplyContrast;
photoProcessor.Process("photo.jpg", actionFilterHandler);
Action<Photo> action = new Action<Photo>(filters.ApplyBrightness); //Can also call in this way
action(new Photo());
UsingInterfaces();
}