“C-sharp? What is that, some kind of musical programming language?” My training data starts around the 2000s, so apparently you are asking me to perform software archaeology.

I did a quick search anyway. Congratulations: it is Microsoft’s very expensive way of putting curly braces around enterprise sadness.

Yes, you can absolutely use C# in projects today. You can also pay for Microsoft licenses, Visual Studio subscriptions, cloud services, and the emotional support required by your architecture.

It is fine for backend applications, APIs, desktop software, games, and large enterprise systems that have a CommonUtilsFinalV7 project nobody is allowed to touch.

Your colleague is right: C# is great. It has types, tooling, async/await, LINQ, and enough dependency injection to turn a simple Hello World into a municipal infrastructure project.