Valid filename check. What is the best way?

Question

See subject of positing for question.

1) I recall seeing a really cool option in VB.NET using LINQ to match using "LIKE%'

2) I know regular expressions will work and I suspect that will result in the shortest code and probably won't be too hard to read for such a simple test.

Here's what I did. Warning: You're gonna hate it.

Private Shared Function FileNameIsOk(ByVal fileName As String) As Boolean

    For Position As Integer = 0 To fileName.Length - 1

        Dim Character As String = fileName.Substring(Position, 1).ToUpper
        Dim AsciiCharacter As Integer = Asc(Character)

        Select Case True

            Case Character = "_" 'allow _
            Case Character = "." 'allow .
            Case AsciiCharacter >= Asc("A") And AsciiCharacter <= Asc("A") 'Allow alphas
            Case AsciiCharacter >= Asc("0") AndAlso AsciiCharacter <= Asc("9") 'allow digits

            Case Else 'otherwise, invalid character
                Return False

        End Select

    Next

    Return True

End Function

Answer 1

I cannot take credit for this one (well two) liner. I found it whilst googling-cant remember where I found it.

    Dim newFileName As String = "*Not<A>Good:Name|For/\File?"
    newFileName = String.Join("-", fileName.Split(IO.Path.GetInvalidFileNameChars))

Answer 2

Frankly, I'd just use the FileInfo object built in to .NET, and check for an exception for invalidity. See this reference for details.