Design Patterns are the rules of code building. No one is obliged to live in the borders of those rules but, mostly without realizing it we use one of those patterns in our code. I think Design patterns come handy in large scaled projects. It is better to have single method to be used in many places by encapsulating exceptional ones (Strategy Pattern)or to have its own method for each situation (State Machine Pattern). There are Design Patterns (DomainDrivenDesign) for which there are books. Those kind of concepts (patterns) solve complex issues, they come up with multiple versions of solutions for a given problem