How to: Trap System Message Dialog?

[ESmith]

I want to be able to catch the exception thrown when trying to write to a
"locked" Usb drive.

For instance:

private void WriteToUsbDrive (string filePath, byte[] theBytes)
{
...
try
{
File.WriteAllBytes (filePath, theBytes);
}
catch (Exception ex) // Just for the example, assume only IO errors
occurred because the key is locked
{
MessageBox.Show ("Unlock the key!!!");
}
}
Testing on Vista, the system dialog will popup first telling the user that
the drive is locked, after clicking away that dialog, my dialog will then
appear - how can I prevent the OS system's dialog from appearing?

TIA

[Peter Duniho]

On Fri, 20 Jun 2008 05:03:54 -0700, ESmith <el**********@hotmail.com>
wrote:

[...]
Testing on Vista, the system dialog will popup first telling the user
that
the drive is locked, after clicking away that dialog, my dialog will then
appear - how can I prevent the OS system's dialog from appearing?

I haven't tried this specifically with a "locked USB drive", but I suspect
that "locking" the drive just makes it read-only. So you should be able
to just check for it being read-only before you try to write to it.

If I recall correctly, there's an unmanaged API that controls whether
Windows presents an error message before failing an operation, but I
haven't used it since Windows 95. I'm not sure it'd even still be
supported. To some extent, if checking for read-only status isn't
suitable for your purposes, you probably should just trust the OS to deal
with things correctly. The question as to whether an error will be
presented to the user when a write to some device fails is really more a
contract between the user and the OS. An application intervening or
voiding that contract should do so only in the most unusual situations.

Pete

[Jeroen Mostert]

Peter Duniho wrote:

On Fri, 20 Jun 2008 05:03:54 -0700, ESmith <el**********@hotmail.com>
wrote:

>[...]
Testing on Vista, the system dialog will popup first telling the user
that
the drive is locked, after clicking away that dialog, my dialog will then
appear - how can I prevent the OS system's dialog from appearing?

I haven't tried this specifically with a "locked USB drive", but I
suspect that "locking" the drive just makes it read-only. So you should
be able to just check for it being read-only before you try to write to it.

If I recall correctly, there's an unmanaged API that controls whether
Windows presents an error message before failing an operation, but I
haven't used it since Windows 95. I'm not sure it'd even still be
supported.

SetErrorMode(). And yes, it still works fine. Though whether any SEM_ flag
has an effect on these particular dialog boxes is an open question.

--
J.
http://symbolsprose.blogspot.com