Business logic is the core application behavior that applies domain rules, makes decisions, and performs processes. In ASP.NET Core, framework code handles networking, handlers receive requests, and business logic performs the application work. It may use databases or remote APIs without depending directly on ASP.NET Core. section 1.1
Keep business logic separate from HTTP-facing handlers:
- Place domain behavior in C# classes or services rather than Razor Pages or API controllers. section 1.1 section 36.2
- Let handlers validate requests, call business logic services, and return or redirect to the appropriate result. section 36.2
- Extract logic into services to improve testability and reuse, especially as an application grows beyond a tiny example. section 12.4
RecipeService
A recipe application can place its business logic in a RecipeService. The service queries recipes, creates new recipes, and modifies existing ones, while page handlers or API controllers coordinate the HTTP interaction. section 12.4 section 36.2
Figure 1.1 A typical ASP.NET Core application consists of several layers. The ASP.NET Core framework code handles requests from a client, dealing with the complex networking code. Then the framework calls in to handlers (Razor Pages and Web API controllers, for example) that you write using primitives provided by the framework. Finally, these handlers call in to your application’s domain logic—typically, C# classes and objects without any dependencies that are specific to ASP.NET Core.
Use the layered application diagram to trace a request from ASP.NET Core networking through handlers to framework-independent domain logic. section 1.1
