New Path APIs in 2.1

NewPath.cs

namespace System.IO
{
    public static class Path
    {
        public static ReadOnlySpan<char> GetExtension(ReadOnlySpan<char> path);
        public static ReadOnlySpan<char> GetFileName(ReadOnlySpan<char> path);
        public static ReadOnlySpan<char> GetFileNameWithoutExtension(ReadOnlySpan<char> path);
        public static bool HasExtension(ReadOnlySpan<char> path);
        public static bool IsPathFullyQualified(ReadOnlySpan<char> path);
        public static bool IsPathRooted(ReadOnlySpan<char> path);

        // Unlike the string overloads, GetPathRoot/DirectoryName will not normalize separators
        public static ReadOnlySpan<char> GetPathRoot(ReadOnlySpan<char> path); 
        public static ReadOnlySpan<char> GetDirectoryName(ReadOnlySpan<char> path);
 
        // Unlike Combine(), Join() methods do not consider rooting. They simply combine paths, ensuring that there
        // is a directory separator between them.
        public static string Join(ReadOnlySpan<char> path1, ReadOnlySpan<char> path2);
        public static string Join(ReadOnlySpan<char> path1, ReadOnlySpan<char> path2, ReadOnlySpan<char> path3);
        public static bool TryJoin(ReadOnlySpan<char> path1, ReadOnlySpan<char> path2, Span<char> destination, out int charsWritten);
        public static bool TryJoin(ReadOnlySpan<char> path1, ReadOnlySpan<char> path2, ReadOnlySpan<char> path3, Span<char> destination, out int charsWritten);

        // This new overload allows resolving the path in a thread safe manner, using the basePath as the effective
        // current directory to resolve paths that aren't fully qualified.
        public static string GetFullPath(string path, string basePath);
        
        // These is not new to 2.1, but it is relatively new and you may have missed it
        public static string GetRelativePath(string relativeTo, string path);
    }
}