C# stays a staple on enterprise and ASP.NET Core teams in the Stack Overflow 2025 Developer Survey. Resumes list “C#” and “.NET” easily; your screen should test how they ship under load. Themes that show up often in r/csharp and r/dotnet hiring threads favor judgment over trivia.
These five questions surface async discipline, DI lifetimes, LINQ execution, production debugging, and tradeoffs, not sealed class quizzes.
1. “When has calling .Result or .Wait on an async method hurt you in production, and why is async void risky?”
Strong candidates describe deadlocks, thread pool starvation, or fire and forget exceptions they fixed. Weak answers recite the async keyword without a scenario.
2. “Walk through Transient vs Scoped vs Singleton with a real ASP.NET Core example, such as DbContext.”
You want lifetime judgment. Good answers explain why Scoped DbContext is the default and how a Singleton holding a Scoped service fails. Weak answers list the three names only.
3. “When does an IQueryable query actually hit the database, and how have you been burned by deferred execution?”
Listen for materialization (ToList, foreach, multiple enumeration) and EF surprises. Strong candidates own a bug where filters ran in memory or twice. Weak answers confuse IEnumerable with “faster.”
4. “Tell me about a production bug you fixed in .NET code (dispose, null, concurrency, or config).”
Past incidents beat definitions. Strong candidates name the symptom, root cause, and the guard they added. Weak answers stay vague or blame “the framework.”
5. “Describe a feature you shipped in C#. What tradeoffs did you accept?”
You learn scope control. Good answers weigh simplicity, performance, and maintainability. Weak answers only list libraries used.
Turn answers into comparable evidence
Log one async pitfall story, one DI lifetime choice, one LINQ or EF surprise, and one shipped tradeoff per finalist.
One scorecard for every finalist
Use the same five questions for each candidate for this opening. Consistent questions support consistent evaluation, which aligns with EEOC guidance for employers to apply the same standards to applicants for the same position (EEOC).
Use Canvider JobCraft to define C#/.NET scope in the JD, InterviewGen for gap-based follow-ups, and DecisionHelper to compare finalists on the criteria you published.
Next step: Explore InterviewGen and DecisionHelper, then get started free.