The provided sample code is a small skeleton C# Web API application. It can be opened and run in Visual Studio 2015. The application manages users and their tasks.

The sample demonstrates a lot of concepts that I consider as "good design practices".

Some key features:

• follows SOLID principles
• embraces DDD concepts
• embraces TDD concepts
• REST API
• low coupling
• uses dependency injection
• code easy to test and mock
• used design patterns: factory, singleton, adapter, composite, decorator, flyweight, template
• DAL is fully decoupled and can easily be replaced (a simple in-memory database is used, but it can easily be replaced with any ORM/NoSql/Object DB, or a combination of all of them)
• domain objects are mapped to database objects, and vise-versa, in DAL (data structures can differ)
• domain objects are mapped to DTO objects, and vise-versa, in services (data structures can differ)
• "Request-Response" pattern in services
• "Common" components are generic, domain agnostic and can be reused in multiple projects