.NET is now cross-platform.

http://news.microsoft.com/2014/11/12/microsoft-takes-net-open-source-and-cross-platform-adds-new-development-capabilities-with-visual-studio-2015-net-2015-and-visual-studio-online/

They throw around terms like open-source, but that doesn't usually mean what you want it to when MS says it, so who knows. There's also a free version of VS for small teams which is apparently feature-complete or nearly so.

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That sort of thing is stylistic. A big reason Java is so much worse than C# despite being similar syntactically is that stuff like that has been baked into the libraries. The C# libraries themselves aren't "architect driven" and don't have that problem.