valid regular regular expression string

Hi I have a regular expression which is strated failing now. not sure what is stopping.

Regex regex = new Regex(@"^(([a-zA-Z]:)|(\\{2}\w+\\[\w- ]+[$])|(\\{2}\w+))(\\[\w-. ]*)*(.xml|.XML)$");

if (!regex.IsMatch(fuSource.PostedFile.FileName))
{
      Page.Validators.Add(new ValidatorHelper("Please select a valid Application XML input file."));
}

the file name i am passing is:

XX2 03-01-2017.xml

But for some reason it is not taking.

please help with the valid file name that matches the pattern..

You can test your regex on an online tool like this one to try it yourself :
https://regex101.com/r/UX9TjE/1

Basically your regexp matches 3 parts in the filename :

• The prefix : It can be 3 things
  • A windows-like drive name : c: or Z:
  • A windows shared drive with parameter : \\shared\user$
  • A windows shared drive : \\shared
• The name (note: it can be empty, ie zero-length) :
  • It includes the path of the file, using backslashes, and it can have spaces :
  • \my\path\my file
• The extension : .xml or .XML

IMHO this regex is not very good, here are some example matches :

c:\path\\XX2 03-01-2017.xml

\\nas\user$\XX2 03-01-2017.xml

\\network_shared\.xml

\\a.XML

You can see why each one matches here :
https://regex101.com/r/UX9TjE/2