mcs
Mono C# Compiler.
TLDR
Compile the specified files
$ mcs [path/to/input_file1.cs path/to/input_file2.cs ...]
Specify the output program name
$ mcs -out:[path/to/file.exe] [path/to/input_file1.cs path/to/input_file2.cs ...]
Specify the output program type
$ mcs -target:[exe|winexe|library|module] [path/to/input_file1.cs path/to/input_file2.cs ...]
