Setting fileIOPermissions for saveFileDialog

Question

I have always had trouble in this area.

I am running on Vista, and I have an application I am developing that needs to be able to save a file anywhere the user selects (i.e. 'c:\').

I can call the savefiledialog, but I always get a permisisons error (even though I'm an admin on this machine) when I select the root folder.

How do I get around this? I've looked and tried this code:

        Dim f As New Security.Permissions.FileIOPermission(Security.Permissions.FileIOPermissionAccess.AllAccess, "c:\")
    f.Assert()

It seems to have no affect. I really don't know what I'm doing here and could really use some pointers.

Thanks.

Marshall