How to combine paths by preserving the original path's directory separator in C#?

Question

If we have /TestDir as an example path, yet we are on a Windows machine, using Path.Join, or Path.Combine with NextDir will yield /TestDir\NextDir.

Is there a way to make it so that if the path I'm appending it to, uses a given separator - the combined path uses the same separator? (Unix/Windows), that is:

• \TestDir with NextDir to yield \TestDir\NextDir.
• /TestDir with NextDir to yield /TestDir/NextDir.

The first directory will always be a rooted path, meaning it will always contain the path separator to use. The only edge-case is network paths, as they always start with \\ but after that they differ in Unix/Windows? Correct me if I'm wrong on this.

EDIT: I've been told that : is the path separator for Classic Mac - is this true? I don't see any .NET API's that treat this as a directory separator.

Answer 1

This will take the first character (either / or \) that it sees and it will replace all other occurrences of / or \ with the first one that it found.

using System;

public class Example
{
   public static void Main()
   {
      char[] separators = { '\\', '/' };
      string path = "/TestDir\\NextDir\\AndTheNext/AndTheNext/AndTheNext\\AndTheNext";
      int index = path.IndexOfAny(separators);        
      path = path[index].ToString() == "\\" ? path.Replace('/', '\\') : path.Replace('\\', '/');
      Console.WriteLine(path);
   }
}

Check it out running here: https://dotnetfiddle.net/fenzWO

Answer 2

Path class uses a field with the name of: PathSeparator, this one depends on OS and is readonly, so that it's easier to create your own class that performs the same actions than Path but you are able to change the value of PathSeparator.

For more information about Path you may read the docs: https://learn.microsoft.com/en-us/dotnet/api/system.io.path?view=net-5.0