The issue with C# specifically is dataset availability. Open source C# code on GitHub is a fraction of Python/JS, and Microsoft hasn't released a public corpus the way Meta has for their code models. You'd probably get further fine-tuning Qwen3-Coder (or a similar base) on your specific codebase with LoRA than waiting for a dedicated C#-only model to appear.
Fine-tuning / LoRA on basis the org code base would be make it more useful.