Will string.Trim() ever remove *valid* characters from a filename?

Question

I'm creating a class to store a filename. To do so, I need to know exactly which characters are invalid and exactly which characters are invalid as leading/trailing characters.

Windows Explorer trims leading and trailing white-space characters automatically when naming a file, so I need to trim the same characters when constructing a filename instance.

I thought about using string.Trim(), but it would be naive to assume the default set of characters it trims coincides exactly with the invalid leading/trailing filename characters of the OS.

Documentation for string.Trim() says that it trims the following characters by default: U+0009, U+000A, U+000B, U+000C, U+000D, U+0020, U+0085, U+00A0, U+1680, U+2000, U+2001, U+2002, U+2003, U+2004, U+2005, U+2006, U+2007, U+2008, U+2009, U+200A, U+200B, U+2028, U+2029, U+3000, U+FEFF

Unfortunately, some of the above characters are NOT invalid in a file, because they aren't in the character set returned by System.IO.Path.GetInvalidFileNameChars.

Am I then correct that string.Trim() could potentially remove VALID leading/trailing characters from a filename, therefore corrupting the filename?

What exactly are the invalid leading/trailing characters for a filename in the Windows Vista OS? I understand that they are not necessarily the same as the file system itself, since the OS can run on different file systems.

Answer 1

Am I then correct that string.Trim() could potentially remove VALID leading/trailing characters from a filename, therefore corrupting the filename?

Yes. Even more so on a UNIX-like system, where ' X' is a valid filename and distinct from ' x '

Answer 2

Filenames can start/end in spaces. Trim will eliminate them.

File names cannot contain

/ \ : * ? " | < >

Answer 3

This code runs and creates the file:

Imports System.IO
Module Module1

Sub Main()
    Dim fs As New FileStream("d:\temp\   file . foo ", FileMode.Create, _
       FileAccess.Write)
    'declaring a FileStream and creating a word document file named file with
    'access mode of writing
    Dim s As New StreamWriter(fs)
    'creating a new StreamWriter and passing the filestream object fs as argument
    s.BaseStream.Seek(0, SeekOrigin.End)
    'the seek method is used to move the cursor to next position to avoid text to be
    'overwritten
    s.WriteLine("This is an example of using file handling concepts in VB .NET.")
    s.WriteLine("This concept is interesting.")
    'writing text to the newly created file
    s.Close()
End Sub

End Module

NOTE: the actual name of the file created with the above code appear to be " file . foo". If I edit the filename in Explorer the space isn't there but when I rerun the code above, it replaces the file.

NOTE: I took the code from http://www.startvbdotnet.com/files/default.aspx and added the spaces

NOTE: I notice that Vista's Explorer rename won't let you add the spaces before or after filename, so you can make "foo . txt" but not " foo.txt " using that method.