Before I joined Microsoft I might have vaguely held that idea too and used it in arguments to push back against detractors or reassure someone. I understand its allure. It’s easy to grasp and very easy to repeat. But, working on Roslyn–the complete from-the-ground-up rewrite of both VB and C#–for 5 years, I came to understand how unequivocally false this idea really is. I worked with a team of developers and testers to re-implement from scratch every inch of both languages as well as their tooling in a huge multi-project solution with millions of lines of code written in both. And with so many developers switching back and forth between them, and a high bar for compatibility with the outputs and experiences of previous versions, and the need to faithfully represent every detailed nuance throughout a massive API surface area I got to be intimately familiar with the differences.

This list is not exhaustive. It’s exhausting. It’s not all the differences there are, it’s not even all the differences I’ve ever known, it’s just the differences I can remember off the top of my head until such time as I become too tired to go on; until I’m exhausted. If I or others run into or remember other differences I’ll gladly update this list after the fact.