Will there be a big mistake if you do not divide into projects?

Question

ASP.NET

Good afternoon/evening!
In the aspnet mvc arch
example, there is a division into projects.
Is it a mistake to split into subfolders instead of projects?

Answer 1

Of course, there will be no mistakes: every architecture has the right to life.
But if you break it into projects with proper use of interfaces and dependency injection, then in the future it will make it easier to add new functionality / rewrite existing ones.
For example, if you take out all interaction with the database in a separate project, then in the future, if the type of the database suddenly changes or, for example, you switch from MySQL to regular files, then it will be enough to add a separate project, write logic and change the implementation class in the dependency injection container instead of in order to rewrite an existing project, partially breaking the functionality and creating new crutches. The principle of modularity from SOLID in all its glory.
Well, on the topic, you can read " Dependency Injection in .NET"