[HOWTO] Using Path.Combine correctly to ensure cross-platform compatibility

I guess every .NET developer is familiar with the Path.Combine method. But, is every .NET developer using it correctly to ensure its result is cross-platform compatible? I guess no as I was one of these developers who didn’t use it correctly.

Did you ever see something like this?

var arbitraryPath = Path.GetFullPath(
  Path.Combine(
    AppContext.BaseDirectory,
    @"..\..\..\..\ArbitraryDirectory"
  )
);

This works flawlessly on Windows. However, it fails on Linux.

System.IO.DirectoryNotFoundException : Could not find a part of the path '/home/vsts/work/1/s/src/WhateverProject/bin/Release/net10.0/..\..\..\..\ArbitraryDirectory'.

To make use of the full potential of Path.Combine make sure to let the method decide which delimiter to use based on the underlying operating system by using it properly!

var arbitraryPath = Path.GetFullPath(
  Path.Combine(
    AppContext.BaseDirectory,
    "..",
    "..",
    "..",
    "..",
    "ArbitraryDirectory"
  )
);