Does anyone know of a C# code formatter that works for oxide plugins? I want to beautify some one lined .cs files.

There is nothing different about Oxide plugins. Any C# code formatter/beautifier would work.

There are 2 online C# formatters that I tried.

.cs(178,77): error CS1525: Unexpected symbol )', expecting ,' or `;'
.cs(182,76): error CS1525: Unexpected symbol )', expecting ,' or `;'​

You may run into that regardless, they can only do so much sometimes.