Directory.GetDirectories returns wrong results with a pattern of *.* [duplicate]

Question

Assume you have a directory that contains the following directories:

dontgetme
get.me

If you use the following code:

string[] directories = Directory.GetDirectories(rootDirectory, "*.*", SearchOption.TopDirectoryOnly);

You would expect directories to contain:

get.me

But it contains both directories, why is this?

Looking into the documentation the only wildcards are * and ? so they shouldn't be affecting this.

Further if you use the pattern *. only the dontgetme directory is returned; but using *.*.*.* etc. both are still returned.

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In case it matters I am using .NET 4.6.1 and C# 6 on Windows 10.

Answer 1

You pattern means "anything with any extension". No extension is "any extension", so you match all four.

You could try ?*.?* as pattern so you get those that have at least one character as both extension and name.

Answer 2

Windows file and directory names always have an extension, even if it's blank. So *.* matches anything because it's treated as anything.