Loads a dialog from a resource file into memory. If the resource file name is NULL, creates an empty dialog.

Note: The dialog name specified in the resource file must match both 'resource' input argument and the name of the resource file without name suffix. 'session_dialog_name' input argument can be anything. It's important that Pro/TK apps a. use dialog resources whose resource names do not clash with PTC-defined resources b. use dialog instance (session) names which also do not clash with PTC-defined instance (session) names. The usual approach to ensure uniqueness in this context is to make sure both Dialog resource and instance (session) names make use of a prefix pertaining to the name of the Pro/TK app.