using System;

using System.IO;

public class Program

{

    public static void Main()

    {

        Uri file = new Uri(@"Z:\Dropbox\Amber Optix Image Store\COV\BioHV\Line batches\2022 02 28\TEST005191 (MV results applied)");

        Uri folder = new Uri(@"W:\Dropbox\Amber Optix Image Store\COV\BioHV\Line batches\");

        string relativePath = 

            Uri.UnescapeDataString(

                folder.MakeRelativeUri(file)

                    .ToString()

                    .Replace('/', Path.DirectorySeparatorChar));

        Console.WriteLine(relativePath);

    }

}

​