In this article, we are going to explore the classic specification pattern and implement it in order to compose the LINQ queries, and also non-LINQ queries. This article will also help beginners in understanding the specification pattern and how to implement it in practice. Major benefits of the specification patterns include reusability, maintainability, loose coupling of business rules from the business objects, readability and easy testing.
Specification pattern as per the definition from Wikipedia, is a particular software design pattern, wherebybusiness rules can be recombined by chaining the business rules together using boolean logic. To put it simply, business rules are segregated based on the Single responsibility principle (SRP) and chained or composed using boolean operands (AND, OR or NOT) to achieve the desired result. Each segregated business rule is called Specification.
Each specification inherits the
CompositeSpecification class which defines one
IsSatisfiedBy. This method is the engine of specification pattern. The responsibility of this method is to apply the business rule (specification) on the object in question and return a boolean result. The primary goal of the specification pattern is to select the subset of objects that satisfy a set of specifications chained together.