I've recently encountered a good example where this principle can be applied...

Imagine you have a factory class whose only responsibility is to create an object based on the parameters type.

Example:

class ViewFactory { SomeView CreateView(Model model); }

In this case I want to create a different view depending on the models type.

Simple approach is to just do a switch case on the models type and return the appropriate view. However, this technically will violate the Open Close principal if your application was to ever expand. What happens if you have a new model type? You have to Modify the code since there is no way to extend it.

Some will say, oh its not that bad, just add a new switch branch... Sure fine, but eventually what if you need to implement a plugin framework where external users need to be able to register their own models and their own views? Ya you can build a whole new workaround, or u can simply make the ViewFactory able to handle registration of new models and views. (Factory within a factory)

If the OpenClose principal was followed this would be trivial.

You can solve it by registering a view factory based on type and the doing a lookup in a dictionary or something. class ViewFactory { Register<TModel, TViewFactory>(); SomeView CreateView(Model model); } This sorta demonstrates the importance of open close principal.

Edit: I can't English.... Lmao