What is the standard way to handle users opening incorrect file types?

Question

I hope my Q was clear ... I am curious about the typical way to code for someone clicking File|Open, and selecting a file that is inappropriate for the program--like someone using a word processing program and trying to open a binary file.

In my case, my files have multiple streams streamed together. I'm unsure how to have the code validate whether an improper file was selected before the app throws a stream read exception. (Or is the way to handle the situation to just write code to catch a stream read exception?)

Thanks, as always.

Answer 1

Magic number at the start of the file generally helps -- if you have control of the file format.

Otherwise, yeah -- catch the exception and put up a dialog.

Answer 2

I think it's quite usual that you have code that just tries to open the file, and if it fails, an error is shown to the user. Most file formats has some kind of header with a "magic number", so that the reader can tell if it's not the right file very quickly after reading the first few bytes of the file.