Search for a file in the directory tree

PathWalker.cs

using System;
using System.IO;
using System.Linq;

static class PathWalker
{
    public static string Find(string filename, string path)
    {
        if (filename == null) throw new ArgumentNullException(nameof(filename));
        if (path == null) throw new ArgumentNullException(nameof(path));

        var directory = new DirectoryInfo(path);

        while (true)
        {
            var file = directory.EnumerateFiles(filename).FirstOrDefault();

            if (file is not null)
            {
                return file.FullName;
            }

            directory = directory.Parent ?? throw new ArgumentOutOfRangeException(nameof(filename), filename, "Unable to find file in path");
        }
    }
}