* C# is statically typed and compiled, which means a lot of problems the would be runtime errors in a Ruby on Rails project will be caught before deployment at compile-time.
* Being compiled also means theres a lower overhead to running C# code - there's no interpreter overhead.
* Anecdotally, many large sites (e.g. Twitter) that used the Rails stack have complained that the technology behind the site caused problems when they grew. Conversely, Stack Overflow, a large site using the ASP.net stack has never complained that C# was a problem in their growth. Correlation not causation, maybe, or perhaps the "Rails doesn't scale" mantra came about for a reason.
* Visual Studio is probably hand down the best IDE out there with good reason - Microsoft is heavily incentivised to keep developers using the Microsoft stack so making it hard or undesirable to abandon their development environment is important for it.
* Being compiled also means theres a lower overhead to running C# code - there's no interpreter overhead.
* Anecdotally, many large sites (e.g. Twitter) that used the Rails stack have complained that the technology behind the site caused problems when they grew. Conversely, Stack Overflow, a large site using the ASP.net stack has never complained that C# was a problem in their growth. Correlation not causation, maybe, or perhaps the "Rails doesn't scale" mantra came about for a reason.
* Visual Studio is probably hand down the best IDE out there with good reason - Microsoft is heavily incentivised to keep developers using the Microsoft stack so making it hard or undesirable to abandon their development environment is important for it.