Brief instructions on how to install C# 

C# can be obtains in various for different platforms.  There are 3 main options

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1.
If you have a recent version of Windows, C# comes with the .Net
framework.  It must be downloaded for early versions (XP).  .Net 4.0
or later version is recommended.  get the full version, not just the
"client profile".  When downloading, make sure you get the "sdk" package
which supports development.

Once installed, find the folder that contains the file csc.exe, which is
the C# compiler.  This is going to be something like
C:\Windows\Microsoft.Net\Framework\v4.0.30319\

Now go to control panel - system - advanced - environment variables.

Edit the system variable PATH (find in bottom window) to include the
above directory.  The directories are separated by ;

Now you can write a C# program using some editor, go to the command
line prompt and type csc program.cs to complie program.  You'll get a
program.exe if compilation is successful which you can then run
directly: type program.exe or .\program.exe

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These instructions are approximate - they may differ a little depend on your
windows version.  You should be able to figure things out yourself from here.

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2.

***** Another option, which is available for windows as well as Linux and 
MacOS, is goto

https://www.microsoft.com/net/core#windowscmd

And download .Net core sdk for your appropriate platform and follow the 
simple example, EXCEPT:

type 'dotnet build'  TO COMPILE  (don't run without compiling separately)
type 'dotnet run' to run

I've only tried this on windows and I haven't figured out how to invoke
the C# compiler independently of the "dotnet" script.  It's intended for
Visual Studio users but of course it's possible to get around it.  You 
can experiment with the latest C# features this way, but most of the really
important language enhancements are available from .Net 4.0 onward.


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3.

you can also use Mono, which was intended for Mac/Linux but
also can run on windows.  This is the recommended option for Macs.
http://www.mono-project.com/download/

mcs program.cs  (compiles)
mcs -t:library lib.cs    (creates .dll)
mcs program.cs -r:lib.dll  (uses .dll)
mono program.exe  (runs)

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4. 
Microsoft has developed its own version of .Net "Core" for Mac, Linux.  When
I tried this last year there were some problems, and I don't know if they've
been fixed.  So I can only recommend Mono for Mac and Linux.


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5. 
If you have Visual Studio (free "community" version available) you can use that. HOWEVER, BE SURE TO COMPILE AND RUN SEPARATELY!  

IDE User: "duh, why should I do that when I can build and run with one click?!"

Me:  "duh, just because you can do that doesn't mean there's no difference
      between compiler errors and runtime errors. Can you tell the difference?"

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