Error message from compiler:
Mono C# compiler version 126.96.36.199
mcs -out:main.exe main.cs
main.cs(2,14): error CS0234: The type or namespace name
UI' does not exist in the namespaceSystem'. Are you missing an assembly reference?
main.cs(4,13): error CS0246: The type or namespace name
TextWriter' could not be found. Are you missingSystem.IO' using directive?
There's a few reasons why it shouldn't work.
- repl.it is a terminal-based site. There is no UI involved.
- System.UI doesn't even exist.
- If you meant to use Windows.UI, you can't because repl.it runs on Linux.