Additional Principles

DRY, KISS, YAGNI, separation of concerns, cohesion, coupling, Law of Demeter, Tell Don't Ask, fail fast, least astonishment, convention over configuration.

1. What does DRY really mean, and when does removing duplication make a .NET codebase worse?

   Don't Repeat Yourself as single source of knowledge, not identical text; accidental versus true duplication; the wrong abstraction; where DRY matters most.

   Mid-Level Theory Additional Principles · 🔗 3 follow-ups · 🛠 1 real-world
2. What does KISS mean in practice for a .NET engineer, and how do you tell simple from merely easy?

   Keep It Simple: essential versus accidental complexity, simple versus easy, readable code over clever code, and how to argue for simplicity in design reviews.

   Mid-Level Theory Additional Principles · 🔗 3 follow-ups · 🛠 1 real-world
3. What is YAGNI, and how do you balance it against designing for future requirements?

   You Aren't Gonna Need It: costs of building speculative features, the difference between speculative features and keeping options open, and reversible versus irreversible decisions.

   Mid-Level Theory Additional Principles · 🔗 3 follow-ups · 🛠 1 real-world
4. What is Separation of Concerns, and how does it show up in an ASP.NET Core application?

   Separation of Concerns at method, class, project and service level; layers versus vertical slices; cross-cutting concerns via middleware and filters; the cost of over-separation.

   Mid-Level Architecture Additional Principles · 🔗 3 follow-ups · 🛠 1 real-world
5. What is high cohesion, how do you recognise low cohesion in C# code, and how do you improve it?

   Cohesion as how strongly the parts of a module belong together; types of cohesion; symptoms such as utility classes and feature envy; measuring with LCOM; refactoring by feature.

   Mid-Level Theory Additional Principles · 🔗 3 follow-ups · 🛠 1 real-world
6. What does low coupling mean, what kinds of coupling exist in .NET systems, and how do you reduce the harmful ones?

   Coupling as the degree of dependency between modules; types from content to data coupling; temporal, deployment and database coupling in distributed systems; techniques to reduce it.

   Senior Architecture Additional Principles · 🔗 3 follow-ups · 🛠 1 real-world
7. What is the Law of Demeter, and how do you apply it in C# without banning fluent APIs and LINQ?

   Principle of least knowledge: talk only to immediate collaborators; train-wreck chains; why fluent builders and LINQ are not violations; refactoring by moving behaviour.

   Mid-Level Theory Additional Principles · 🔗 3 follow-ups · 🛠 1 real-world
8. What does Tell, Don't Ask mean, and how does it change the way you design domain classes in C#?

   Tell objects what to do instead of querying state and deciding outside; anaemic versus rich models; invariants; where querying is fine (CQRS reads, DTOs).

   Mid-Level Theory Additional Principles · 🔗 3 follow-ups · 🛠 1 real-world
9. What does fail fast mean in .NET, and how do you apply it without making the system fragile?

   Detect invalid state at the earliest point: guard clauses, ArgumentNullException.ThrowIfNull, options validation on start, ValidateOnBuild; fail fast versus resilience at boundaries.

   Mid-Level Theory Additional Principles · 🔗 3 follow-ups · 🛠 1 real-world
10. What is the principle of least astonishment, and how do you apply it to C# APIs and library design?

    Code and APIs should behave as users expect: naming, side effects, .NET conventions (Try pattern, Async suffix, CancellationToken last), equality, exceptions and defaults.

    Mid-Level Theory Additional Principles · 🔗 3 follow-ups · 🛠 1 real-world
11. What is convention over configuration, and where does .NET use it in ASP.NET Core and EF Core?

    Sensible defaults that remove boilerplate: EF Core key and relationship conventions, ASP.NET Core routing and configuration conventions; overriding defaults; risks of hidden magic.

    Mid-Level Theory Additional Principles · 🔗 3 follow-ups · 🛠 1 real-world