Since I haven't see many new Windows apps the recent years, who is actively developing new apps in C# and if yes, what kind of apps, which platforms, etc.? Is it mainly games?
On all enterprise customers that we work with, think DAX, if the application is to run native on the desktop, which is usually means Windows workstations, the software stack tends to be .NET with some C++ here and there.
Sun never managed to understand the desktop and Oracle even less.
So unless the customer has requirements for portable desktop applications, the solution is .NET.
Almost everybody doing in-house enterprise desktop apps (and those are a heck of a lot) and tons of people doing desktop Windows apps that don't need to be C++ (e.g. not Photoshop, Office and co).
Again, those are in the tens or hundreds of thousands. Check any Windows app review site or repo for examples.
It is _massively_ faster to write a quick UI in .Net than it is to write one in HTML.
I have been doing WPF development in the last two years for enterprise customers.
Also as a Windows user, there are plenty of applications to choose from.
C# and .NET used to be tied to Windows and IIS, Microsoft's web server, but recent developments are making it possible to create self-hosted applications and services written in C# that run in Linux. The self-hosting functionality is fairly mature by now, but the Microsoft implementation of cross platform C#/.NET is very early in its development.
It'll be interesting to see if Linux becomes a popular environment for developing and hosting .NET applications.I predict that it will be used, but it won't overtake the widely-used open-source alternatives such as Ruby, Python, and Node.js.
It's very easy to use C# to develop Windows services. I've written a few Windows services with C#, and it was pretty simple.
The typical model for most of our applications is we have three components - background agent, UI, and database. The UI handles configuration, user management, controls starting and stopping of processes, and also handles incoming API calls. The background agent is usually a windows service and the database is usually SQL Server.
Our products are used by hospitals as installable products and also by software vendors as libraries and bolt-on applications.
My condolences.
Anecdotally I have some friends writing business software at various BigCo companies that use C#.
Edit: it's perhaps worth mentioning that there is some more nuance to the Unity situation with their IL2CPP tech. Bottom line: engine users are writing C#.
BTW, here's the third-party C# Windows app I use most often: https://windows.github.com/