How Should I Prepare for a C# Interview at a Company With Proprietary Software?

August 29, 2026 4 answers
Asked by MellowBirch42
I recently completed an HR screening for a software development role, and the recruiter scheduled a technical interview with the development team. They mentioned that much of the company's software is proprietary and that new hires need time to learn it. The team primarily works with C#, SQL, Python, React.js, and some VBA, with C# being my strongest and most comfortable language. What topics or types of exercises should I practice beforehand, and how can I prepare for working with an unfamiliar internal codebase?

Answers

CopperWren36
Since C# is your strongest language, review core .NET and C# concepts, object-oriented design, exception handling, collections, async code, and basic application architecture. It would also be worth reviewing SQL joins, filtering, grouping, and writing queries without relying too heavily on a visual query builder. A little familiarity with deployment practices, DevOps, and service-based architecture could help too.
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QuietCactus91
โ€œProprietaryโ€ usually just means the software was built internally or heavily customized, so they probably arenโ€™t expecting you to know it already. Theyโ€™re more likely looking for someone who can explore an unfamiliar codebase, make reasonable assumptions, ask good questions, and explain their thinking clearly. Practice reading messy or unfamiliar C# projects and tracing how the pieces fit together.
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NorthStarMilo5
The technology list suggests the role may involve maintaining a fairly custom or older system, so ask what โ€œproprietaryโ€ actually means in practice. Find out whether the interview focuses on building something new, fixing an existing bug, or understanding their architecture. Some companies use that term for perfectly manageable internal tools, while others have old generated code and limited documentation, which can make the day-to-day work very different.
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PixelHarbor7
Ask the recruiter what format the interview will take. It could involve computer science concepts, live coding in a language you choose, debugging existing code, pair programming, or a data-structures exercise. Knowing the format is much more useful than guessing what the companyโ€™s proprietary tools might be like.
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