C# & .NET, from the Inside: The Roadmap

I write C# and .NET every day. I can ship an API, model a domain with Entity Framework and get it into production. But using a language every day and mastering it are two different things, and the gap shows where it matters most: a senior-level code review, a performance problem nobody can explain, or an interview where "it works" isn't the answer the interviewer is looking for.

This series is how I close that gap.

Why now

I'm working toward senior roles, including international ones. A senior interview doesn't check whether you know what a record is. It checks whether you know what the compiler generates for it, when value equality becomes a trap, and why you would pick a record struct instead. I want to answer those questions from experience, not from memory.

How this series works

• Learning in public. I follow a structured roadmap, Anton Martyniuk's .NET Senior Playbook, and write about the topics where I have something of my own to show.
• Past the definition. Each article starts from a real question or mistake and goes further: what the runtime actually does, where the edge cases are, and how it plays out in production code.
• Sources you can check. I verify every explanation against the official Microsoft documentation and the articles I read along the way. Each article ends with its references.
• Code you can run. Every claim comes with a snippet you can paste into a console app. When I talk about performance, I measure it with BenchmarkDotNet and show the numbers.
• Real projects. Where it fits, I apply the ideas in my own projects and report what changed.
• One idea per article. No chapter summaries. If I have nothing to add to a topic, I skip it.

Stage 1: C# language fundamentals

The foundations everyone "knows", and the details that separate knowing from mastering:

• Types and the type system: what really lives on the stack and the heap, what boxing costs, and when a struct beats a class.
• Operators, statements and expressions: operator overloading done right, and the null-handling operators that hide more logic than they seem to.
• Object-oriented C#: inheritance or composition, interfaces or abstract classes, and when to seal a type.
• Records, anonymous types and tuples: what the compiler generates behind them, and when value equality surprises you.
• Generics and variance: constraints, why IEnumerable<T> is covariant but List<T> isn't, and generic math.
• Collections: picking the right collection for the job, and which interface to expose from an API.

What comes next

Stage 1 is the start. Later stages go into functional C# and LINQ, async and memory, the runtime itself, and then ASP.NET Core in production. I'll fill in each stage here as I reach it.

Who it's for

Developers who already use C# and want to understand it, not just use it, and anyone preparing for mid senior .NET interviews. If you spot a mistake or have a better example, tell me: learning in public only works if the corrections are public too.

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Written by Ayoub Edahlouli. The path follows Anton Martyniuk's .NET Senior Playbook; the explanations, code and benchmarks are my own, checked against the official Microsoft documentation and the sources cited in each article.