C# does not compile to byte code, like java it compiles to an intermediate code, called MSIL, and you’ll need to make sure the .NET runtime is on any machine that wants to run it. Unless C# has a native compile option I am unaware of.
I would never rely on Microsoft if your goal is to be multiplatform compatible, you are shooting yourself in the foot before you get out of the gate if that is your goal.
Your only serious options are a native language like C, C++ etc, and utilizing Macros in your compiler to have one set of source to compile for multiple environments, or Java. Yes, you can use a scripting language like a Python, but this doesn’t resolve your decompiling issues, performance speed concerns, or your need to make sure that the runtime is on the machine.
Java is the only real “language” option you have if you are doing serious stuff. If you are doing things that a scripting language will work for you, Python is fine but you aren’t going to get speed or escape the dependence of needing the run time, or safe compiled code.
If what you are trying to do is something that a scripting language can handle, pick your poison, ones the same as another as far as I’m concerned. If you want a full featured language with cross platform compatability, “write once run anywhere” java is the only serious option. If throughput or low level operations are needed, then you are talking C or C++ or something that compiles directly native language and you’ll need to compile different runtimes for different platforms and keep your source code maintainable with all those differences that may be needed.
Good luck
I’ve been looking at some of the functional languages, like Erlang and Scala and F#, that supposedly will help improve performance on multi-core CPUs. Not sure about Erlang, what I like about Scala, is that it runs on the JVM, and seems to get the best of both worlds (OO and Functional programming).
And of course now with Oracle owning Java, it will be interesting to see what they do with JVM(s), which in the end, matters more than which language is used to generate the byte code.