Do not compete for language, but state the facts:
1. desktop software
Not only Windows, but also open-source Mono, but also C # in Apple Mac and Linux (such as Ubuntu. In addition, the mkbundle tool can be used to separate the C # program from the Mono framework and run on Mac/Linux, just like a program compiled directly using C/C ++.
2. Web Development
In addition to ASP. NET is used to develop large websites and run on Windows, Linux, and FreeBSD. It is applicable to a wider range of enterprise development fields (including but not limited to WF, MOSS, VSTO, BI, and so on ), C # (with Java) based on industrial standards is still the best choice for enterprise development.
3. mobile client
With Xamarin (based on Mono), you can use a set of core code to develop Native applications running on three platforms (WP/iOS/Android.
4. embedded
Based on the. NET Micro Framework (open-source) hardware development (entry), there is a lot to do in the IOT era.
5. Rich internet applications (RIA)
HTML5 is the future, but Silverlight (and Flash) is still indispensable.
6. Game Development
In addition to the Kinect/Xbox games, there are also MonoGame and Unity3D (based on Mono ).
7. Cloud
There are Azure and AWS, enough!
8. To be continued...