Question

I’m maintaining a Windows CE app built with the .NET Framework that has about 45 forms. There are 5 ‘sections’ which lead to the function you want. The application is 100% full screen and it is important that it can’t be minimized.

Since there are so many forms, it’s difficult to keep track of which form should be displayed after one is closed. For this, I’m setting the form owner property before showing it, and showing the owner when closing it.

I’ve also been advised that it is best to instantiate all forms when the application loads, and not dispose them to save processing time. I’m not sure about this.

My question is, what is the best way to go about showing, hiding forms where you want any 1 form to be in front, full screen all time?

Answer 1

I would not go the route of instantiating 45 forms when the application starts. This would severely lengthen the startup time and possibly (if not probably) exhaust your memory resources, all to provide functionality that your user may not even need.

In my WinMo applications, each form is designed to work with a relatively small subset of data, so the startup time is limited to database calls and loading the data into the form’s controls. Typically, the time required to instantiate one of these forms and show it is never more than a second or two.

If your forms are taking longer than this to show, it’s possible that there’s a problem with your data retrieval or with the way the data is loaded into the form’s controls (e.g. you might have a custom gridview control that fully renders all 300 rows even though only 12 are visible at one time). If your data is so large that it legitimately takes a long time to retrieve, chances are that’s far more data than a user can practically interact with anyway.

I assume your mention of “5 sections” to get where the user needs to go means that they might (at a maximum) be “drilling down” 5 levels to something. If you implemented this by having each form instantiate and show the next form using ShowDialog, you would have at most 5-6 forms in existence at any one time, which shouldn’t be any problem for a .Net CF application (I do this all the time). This way, you don’t have to do anything special to keep track of which form should be shown when – you just open a form from wherever, and when the form is closed you’re automatically back to the calling form.

There is some z-order/task manager weirdness that you have to deal with, but it’s not especially complicated. Before calling ShowDialog on the child form, you set the parent form’s Text property to a blank string, and then set it back to the form’s original caption after ShowDialog returns. This isn’t strictly necessary, but in Windows Mobile (at least up to version 6) all open .Net forms (with a non-blank Text property) show up in the Running Programs list, even if they’re all from the same application. I generally like my multi-form applications to appear to be just one program, so I usually set the Text of every form to the name of the application).

I’ve also experimented with a single-form application that implements every piece of UI as a UserControl instead of a Form, and then creates and stacks the controls as if you were creating and opening forms. This works but it’s a hack and I don’t recommend it. Forms have a Load event and UserControls don’t, which is the main problem.