Path.GetDirectoryName returns null on UNC path

Question

Path.GetDirectoryName(@"C:\\");

returns null and

Path.GetDirectoryName(@"C:\\Foo");

returns C:\

While this is exactly the behaviour mentioned in the documentation I'm wondering why

Path.GetDirectoryName(@"\\server.domain.tld\Foo");

returns null and not as I'd have expected \server.domain.tld\

Does anyone have clue why?

Answer 1

Typically, the UNC path structure is \\{server}\{share}\{path.....}, so "Foo" in your UNC example is equivalent to the "C:\" of your first example. This is why you get null for the path of your UNC example.

The path of "\\server\foo\bar" would be "bar"