The target of this post is clean code principles, and other cases investigated in other posts, so some below topics maybe aren't standard or in best practice: Implementation Layers, Implementation Architecture, Business Logic Business workflow, even performance, ...
instead of it, I focused on these topics: 1.Naming 2.SOLID 3.Method Chaining 4.Minimal use of comments 5.Error handling with Polymorphism 6.Avoid Type-Checking 7.Enumeration 8.Side Effects 9.Interpolated Strings And In-line if 10.Code Optimization(Null Coalescing, Expression Body Methods, Switch, ...) ...