How to open a password protected .ppt file with the Microsoft.Office.Interop.PowerPoint

Okay that became part of my solution... since my goal is simply to 'skip' password protected files I was able to attempt to open them with a dummy password and catch the exception and simply report that back to the user.

On the other hand, some of these files are read-only capable and require a password for 'modifications'.   When you open these files by hand you get the dialog that let's you click 'open as read-only' and continue to open and export the document by hand...  I can't figure a way to handle this situation via the interop either... I've tried opening with ReadOnly (goes for office/excel documents too) but it still pops up the dialog, so I have to spawn the process in a Thread and give it a timeout, assuming if it doesn't open then it's probably asking for a password.   I'm ok with this, but wouldn't mind a more robust solution. 

Guess we're stuck without a smooth interop into office, we'll have to live with the one we got for now! 

long story short  here's the rough outline of my solution:

Application powerPoint = new PowerPoint.Application();

Presentations presentations = powerPoint.Presentations;

Thread openPPT = new Thread(delegate() {

presentations.Open("filepath", MsoTriState.msoTrue, MsoTriState.msoFalse);

});

openPPT.start();

if (!openPPT.Join(20000)) // 20 seconds to open

throw new Exception("Can't open, took too long, probably requires password...etc...etc.");

else

// processfile.... 

try/catch around the open to catch the 'invalid password' issue if you want...   use  powerPoint.ProtectedViewWindows.Open with a fake password and it will throw it there...

other options include:

ps = powerPoint.ProtectedViewWindows.Open(request.FilePath, "fakePassword", Microsoft.Office.Core.MsoTriState.msoFalse).Presentation;                            

                            if (!string.IsNullOrEmpty(ps.PasswordEncryptionAlgorithm))

                            {

                                throw new Exception("PowerPoint file requires a password, this cannot convert.");

                            }

Although that seems like a hack, it' been solid so far with the hundreds of sample files I have problems with. 

Thanks,

Justin.