The .NET Developer Interview: What to Expect and How to Prepare

You have an interview coming up — or you want one — and you'd like to walk in knowing what's about to happen. Good news: .NET interviews are surprisingly predictable. This series walks you through the whole loop, one round at a time, with the questions that actually get asked and the understanding you need to answer them well.

The typical interview loop

Companies vary, but most .NET interview processes are a remix of the same five or six stages. Here's the shape of it:

Smaller companies compress this into two or three calls. Bigger ones stretch it across a week. Either way, the same material shows up — which is exactly why you can prepare for it.

What interviewers are really deciding

Here's the secret that changes how you prepare: interviewers are rarely checking whether you know a fact. Facts are cheap. What they're listening for is whether you can reason aloud — take a question, think in front of another human, and arrive somewhere sensible — and whether you know why, not just what.

"Strings are immutable" is a fact. "Strings are immutable, which is why concatenating in a loop allocates a new string every pass, which is why StringBuilder exists" is understanding. The second answer gets offers. Every post in this series is built to give you the second kind of answer.

The rapid-fire screen: a sampler

The screen exists to filter, so the questions are short and the expected answers are one or two sentences. Here are six you should be able to knock back without hesitation:

• Value type vs reference type? Assigning a value type copies the data itself; assigning a reference type copies a reference, so both variables point at the same object.
• What is the CLR? The Common Language Runtime — the engine that loads your compiled code, JIT-compiles it to machine code, and manages memory, type safety, and exceptions.
• What is IL? Intermediate Language — the CPU-neutral instruction set the C# compiler produces, which the CLR compiles to native code at runtime.
• The garbage collector in one line? An automatic memory manager that periodically finds objects nothing references anymore and reclaims them, using generations to make short-lived objects cheap to collect.
• Struct vs class? A struct is a value type (copied on assignment), a class is a reference type (shared on assignment); reach for structs only for small, immutable pieces of data.
• What does using do? It guarantees Dispose gets called on an object when you're done with it — even if an exception is thrown — giving you deterministic cleanup of things like files and connections.

If any of those made you pause, don't worry — the rest of the series unpacks each one properly. The one-liner gets you past the screen; the understanding behind it carries you through the technical rounds.

How this series maps to the loop

Each part of this series targets a specific round:

• Part 2: C# language fundamentals — the value/reference distinction, strings, boxing, interfaces vs abstract classes, records. The core of the C# technical round.
• Part 3: async/await — what await really does, why async void is dangerous, and the famous deadlock question. This one shows up in almost every loop.
• Part 4: collections and LINQ — choosing the right collection, IEnumerable vs IQueryable, deferred execution. Feeds both the technical and data rounds.
• Part 5: ASP.NET Core — middleware, dependency injection, and the web/API round.

If you're earlier in your journey and wondering whether C# was even the right horse to bet on, I've written about why C# is a great first language — spoiler: the fundamentals you learn for these interviews transfer everywhere.

How to prepare: understand and try, don't memorize

Memorized answers collapse under the first follow-up question — and follow-ups are the whole game. Interviewers are trained to probe one level deeper than your answer, and then one level deeper again, until they find the edge of what you know. If your knowledge is a script, the edge is one question away. If it's understanding, you can keep going.

That's why every question in this series comes with a 🧪 Try it exercise: a small experiment you can paste into a console app and watch behave. Running the code does two things memorizing can't. First, it makes the concept stick — you'll remember the deadlock you caused far better than the one you read about. Second, it quietly stocks your behavioral round: "I actually reproduced that deadlock in a test project once" is a war story, and interviewers love war stories because they're evidence you tinker.

An honest note about AI in interviews

You'll wonder about this, so let's address it. Some companies now allow — even encourage — Copilot-style tools during coding rounds, because that's how the job actually works. Others ban them for screening. Ask your recruiter; there's no shame in the question.

But notice what AI assistance changes and what it doesn't. If a tool can produce the code, interviewers shift their attention to the thing tools can't fake: your reasoning. Can you explain why the generated code is correct? Can you spot where it isn't? Reasoning aloud matters more in an AI-assisted interview, not less — which means preparation built on understanding just became more valuable, not obsolete.

Ready?

The loop is predictable, the questions repeat, and the interviewers are looking for reasoning, not recitation. That's a game you can prepare for. Let's start where every technical round starts: with the C# language itself.

Next up: Part 2 — C# Language Questions: Fundamentals They Always Ask.