Windows Mobile- only keeping one form open. Best design question

Question

So I would consider myself a .Net and ASP.NET pro but I am a bit new to Windows Mobile (I am targeting .net 3.5 CF and Windows Mobile 6).

I am creating a data driven application that will have 3-4 tables. I have created a form for each table that allows the user to search through the table.

Each form inheretes from the Main form so that they each have the same Menu.

My question is how do I make sure that only one Window is open. I want to allow the user to go to the menu and choose a table which will open a new form. What I don't want is for the user to open say each form and then when they are done to have to close 3 or 4 windows. Is this possible? If so how do I do it? On a side note is there a better way to do this. I don't want all my logic on one form. So I don't just want to hide and show and panels.

Answer 1

I keep something I call an application hub that everything goes though.

So each menu click will call the applciation hub, and each form will reference it.

Then, when switching form, the application hub needs to keep track of the current form, close it, then load the requested form.

This isn't much code to write, and performs well.

Or...performance wise, keep the application hub idea, and keep the dialogs open. It will perform better that way, rather than having to reload the forms all the time.

Then on shut down, the application hub can check which forms are open (it should have a reference to each running form) and close them for the user.

Answer 2

Instead of having multiple Forms (inherited form mainForm) you could put the table stuff on UserControls and have total control about their Creation/Destruction/Visibility much easier. Use an Interface or a BaseUserControl to implement common functionality.

Answer 3

This article, while not exactly what you are asking, was very helpful when I was redesigning a .NET CF application: Creating a Multiple Form Application Framework for the .NET Compact Framework

My application required a bit of both worlds - I wanted to have a single form open, but also sometimes wanted to stack a secondary form on top of the first (eg. if they go to a Prefs page or some other type of form where they should only ever dismiss it after a moment).

(Pseudo-coding after this)
I created a ViewManager and implemented it as a singleton. When the app first launches, I call ViewManager.GotoForm(frm). This sets the current form to be whatever form I need. Then I immediately call ViewManager.CurrentForm.ShowDialog() - I'm sure there's a better way, but I found I had to call ShowDialog() at SOME point just to get a form to appear.

Subsequent calls to ViewManager can take the form .ReplaceForm or .StackForm. The differences should be fairly intuitive.
What you can also do in a view manager like this is cache forms that aren't being displayed, but probably will be again and have expensive setup costs (for instance, in a data-driven app you might have to query the database to determine the fields or tables to display on a form, and this won't change at runtime).

The trick here is that you never call .Show() or .ShowDialog() anywhere in your application - you route all form navigation through the view manager which handles loading the next instance of your form, disposing of old forms (if not being cached), and dispatching any sort of populate logic if you want to pass new data to a form's UI before it loads.