Previously, I discussed our intention to maintain a separation between Presentation (View Model), Domain, and Persistence entities in our architecture. I talked about some of the difficulties this design decision presents, and how we can mitigate those obstacles using an elegant, methodical entity-mapping strategy. In this blog entry, I build off of that discussion and elaborate on some of the high-level architectural patterns which emerge as a result. This is especially relevant if you are using CQRS, although that is not a prerequisite, and these patterns will apply just as readily to other approaches, including traditional N-layered architectures.

In this blog entry I’ll go over using custom ASP.NET Core middleware to catch various kinds of exceptions so that we can return the proper HTTP status code to the user’s browser. At the Angular side we’ll take advantage of these status codes in order to direct the user to the appropriate pages on an error—an "unauthorized" page or general error page—or simply display a notification. This is one approach to handling server exceptions which are prone to "bubble up" from lower layers of the stack, such as the Application and Domain layers, and elegantly updating the UI.

In this entry, we’ll start to add in more structural elements, namely the authentication components of the UI and Identity Model classes in our Web API. Fortunately, ASP.NET Core and Visual Studio do a lot of this work for us via scaffolding tools. Our main concern is to take this auto-generated code, modify it where needed, and move it into the appropriate layers of our Clean Architecture solution, namely the Infrastructure and Presentation layers.

This is the first in a multi-part series in which I will be building off the Foundational Concepts Series. My objective is to present actual, procedural steps that you can follow and apply to your own web projects using ASP.NET Core. As I present these steps, I will be updating the demo application accordingly, the goal being to evolve it into a working web application by the end of this series.

My objective is to demonstrate that Clean Domain-Driven Design works in modern web applications built on the ASP.NET Core stack. The desired end-product will be a multi-tenant SaaS product which can scale to accommodate complex business logic. I intend to revisit different areas of functionality in future blog series’, at which point we can make it more robust and enterprise worthy.