SOLID principles in .NET revisited part 7: the Dependency Inversion Principle

Introduction

In the previous post we saw the definition of the Interface Segregation Principle. We applied it to a problematic case where a class could not fully implement the IAuthorizationService interface. We then broke up the interface into two parts so that they became more specialised. A consequence of ISP is often a large number of small, very specialised interfaces of 1 or maybe 2 methods. Large, monolithic interfaces are to be avoided as it will be more difficult to find concrete classes that can meaningfully implement all interface methods.

We’ve reached the last letter in the SOLID acronym, i.e. ‘D’ which stands for the Dependency Inversion Principle.

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