Upgrading to Visual Studio 2005

Today I got my copy of Visual Studio 2005 through the post, so I’ve been having a play with that, by upgrading some of my VB.NET 2003 projects. Unfortunately, I got a rather confusing error message from them, and I couldn’t find much info on the web, so I’m documenting it here for other people’s benefit.

The error is something like this:
‘FMain’ is a type in ‘Presentation’ and cannot be used as an expression.
where FMain is the name of my startup form and Presentation is the name of the project. However, there’s no line number given, and I can’t find any code that refers to the form.

If I then go to Project Properties, and check the box for “Enable application framework”, that displays an error message that says “Startup object must be a form when ‘Enable application framework’ is checked.” In my case, the startup object is a form (i.e. it inherits from System.Windows.Form), but if I find a different form that the framework checkbox will accept then that also fixes the compilation error.

You can create a new form, set that as the startup object, then enable the application framework, and this is pretty much guaranteed to work. Once you’ve done that, the “startup object” dropdown list is renamed to “startup form”, and it is filtered to what VB considers to be a valid list.

It turns out that the “Sub New” method in the startup form has to be Public (rather than Friend). That’s the default for new forms, but I’ve been changing that for all of mine in the past, to improve security (“don’t expose any more info than you need to”). Similarly, this Public constructor can’t take any parameters.