Branch by abstraction

The steps

1. The original project was MVC Classic, with the domain layer in the same project as the MVC UI. Unit tests for the domain layer were in a separate test project.
2. Introduce the abstraction. The domain layer moved into its own project behind a clear interface. The unit tests showed it still behaved the same.
3. Point the existing UI at it. The MVC Classic UI was changed to depend on the new domain project.
4. Reuse it for more UIs:
   • a hybrid UI (MVC/Razor Pages hosting Blazor components);
   • a Blazor Server UI.

Projects before and after

Three front ends, one core

The same application layer (models, repository, services, validation) in Timesheet.Core, used by three different UIs:

• MVC Classic
  Controllers and Razor views, full page posts. Also has Microsoft Entra ID sign-in.
• Blazor Serveryou are here
  Interactive components over a SignalR connection, no page reloads.
• MVC + Razor Components
  MVC pages hosting Blazor components (abandoned experiment).

How it's built

• C# .NET, on Azure App Service.
• Each front end has its own Azure DevOps pipeline that runs the unit tests, then deploys.
• Data is held in memory, so changes last only while the app is running.
• Git repository on Azure DevOps