The SOLID acronym describes five object-oriented design principles that, when followed, produce code that is cleaner and more maintainable. The last principle, the Dependency Inversion Principle, suggests that details depend upon abstractions. Unfortunately, typical project relationships in .NET applications can make this principle difficult to follow. In this article, I'll describe how one can structure a set of projects in a Visual Studio solution such that DIP can be followed, allowing for the creation of a SOLID solution. You can download the sample solution and use it as a starting point for your new solutions if you like.