Holy cow, I wrote a book!
A customer reported an apparent inconsistency in the
shell common file dialogs:
The question mark appears to be treated differently from other
invalid file name characters.
I tried to save a file in Paint under the name ?.jpg
but instead of telling me that I had an invalid character in the
file name (as it does with other characters like /
< and |)
or navigating to a new folder (like \ or *),
it appears to do nothing.
Actually, it did do something. You just couldn't tell because
the result of that something was the same as doing nothing.
If you type a wildcard like ? or *
into a common file dialog, the dialog interprets this as a request
to filter the list of files to those which match the wildcard
In this particular example, typing ?.jpg says
"Show me all the single-character files with the .jpg
From the description in the original report,
I gather that the customer's tests took
place in an empty directory (so the filter had no effect).
The customer responded with muted surprise.
I hadn't realized you can type in your own filter in dialog boxes.
How long has this feature existed?
The ability to filter the common file dialog has been around since
the dialogs were introduced in Windows 3.1.