Thanks for the reply! I tried Validating, but that is only thrown, when the NumericUpDown gets the focus or looses it and in similar situations. It doesn't seem to be thrown right before the value is changed wrongly. I also tried KeyDown, but wasn't able to intercept the value the NumericUpDown should take after the Key was pressed if there was no maximum and exchange it for the real value. I solved my problem by enhancing a TextBox to take only hexadecimal numbers, adding a minimum and maximum etc. to it.

I think ILNumerics won some community prices in germany but I don't have any experience with it (I wish I could find some use for such sophisticated math in my work though :(( )

As indicated by a previous user, all you need to do is intantiate the cryptostream class on top of your GZipStream, then use the resulting stream to read/write the serialized data. As far as the password goes, I would try to add some random characters (salt) to your passphrase, then take the SHA256 hash of that new string and use the hash as the key to create a new Rijandael cryptostream which would be used as previously stated. Hope this helps, Sounds like somebody's got a case of the Mondays -Jeff

The common OpenFileDialog can't be modified (At least not without some rather complicated hacking.). I just thought it would be a lot nicer to have one dialog instead of using the common dialog and opening a custom dialog upon closing the common one, to ask the user for all the remaining settings. With my custom OpenDialog filtering is a lot more flexible. I can not only filter files by their ending, but also display them in the listView without it.

I found a solution, but I'm not quite happy with it. I simply pass the string I need to the constructor, when I create an instance of the class. Thanks for the help I'll check it out, it might be the cleaner way of accessing the string I need.