Windows batch file containing self-compiling C# code, automatic .NET path detection. Compiles itself to "filename.cmd.exe" with CSC.EXE from .NET installation. If already compiled, launches the *.exe.

hello_csharp.cmd

/* This section is run in batch file mode
@echo off
REM Based on http://stackoverflow.com/a/13485357
SETLOCAL ENABLEEXTENSIONS
if not exist %0.exe (
    for /f "usebackq tokens=1,3 delims= " %%A in (`REG QUERY "HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\NET Framework Setup\NDP" /s /e /f InstallPath  2^>nul ^| findstr InstallPath ^| sort /R`) do (
        set FrameworkDir=%%B
        goto :found
    )
    :found
    %FrameworkDir%\csc.exe /nologo /out:%0.exe /Reference:%FrameworkDir%\System.Net.dll "%0"
)
goto end
*/
//----------------------------------------------------------------------------
using System;

static class Program
{
    static void Main(string[] argv)
    {
        Console.Write("C# says: ");
        if (argv.Length > 0)
            Console.Write(argv[0]);
        Console.WriteLine();
    }
}
//----------------------------------------------------------------------------
/*
:end

REM ** Run the compiled program
%0.exe "Hello world!"
REM */