GForce

Can anyone give, or point me to, a tutorial on how the system registry works with File Types? The information exists within the System Registry to know which File Extensions are related to which application(s) and the corresponding Launch String for an application to use a file.

For example .XLS Files are typically opened with Microsoft Excel. Somewhere in the system registry is a key that instructs the OS to open the necessary application. It might look something like the following: "C:\Program Files\Microsoft Office\Excel.exe %1". Where %1 is the old DOS reference to the parameter, which in this case would be the .XLS FilePath and Name.

My application is storing and retrieving attachments from an SQL Server DB, and I want to be able to determine whether the client PC can open an attachment by using the system registry.

Aquila

You could look in HKEY_ClASSES_ROOT and see if your particular extension has an OpenWithList with something in it. (No openwithlist or nothing inside it then they can't open it)

GForce

That relies on the application being within the System Path. I would rather use the registry in the manner the OS does and launch the application uisng the string provided in the key. This way if there are necessary switches (command line arguments) for a file type they are included.