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Why do I get "Object is currently in use elsewhere" exception?

Answer 1

A:

As far as I understand, the Application.Run() needs to be specifically called before you show any form, since it starts up the window message loop/pump and basically spawns a separate thread for the UI.

If you don't do that, the form will not be able to process messages or paint.

My suggestion is, load up the main form and have the main form call the splash screen before it does any of its normal FormLoad stuff. If the licensing fails, you can call Application.Exit() and return out of FormLoad, thus shutting down your app before the user can use it.

Edit: Note that the main form will not show until after FormLoad exits, so you don't have to worry about hiding your main form while the splash screen is showing.

Edit 2: I found something worthwhile, using ApplicationContext. You can switch out which form is in the main context, so you can load up your splash screen in an initial application context, and then swap it out once it's loaded. Try this:

public class MyApplicationContext : ApplicationContext {
    SplashForm splashForm;
    MainForm mainForm;

    public MyApplicationContext() {
        splashForm = new SplashForm();
        base.MainForm = splashForm;

    }

    public void RunApplication() {
        // This will show the splash screen
        ThreadPool.QueueUserWorkItem(new WaitCallback(MessageLoopThread));

        // This will perform any miscellaneous loading functions
        splashForm.PerformLoadingFunctions();

        if (!CheckLicensing()) {
            ShowErrorMessage();
            Application.Exit();
            return;
        }

        // Now load the main form
        mainForm = new MainForm();

        // We're done loading!  Swap out our objects
        base.MainForm = mainForm;

        // Close our splash screen
        splashForm.Close();
        splashForm.Dispose();
        splashForm = null;
    }

    private void MessageLoopThread(object o) {
        Application.Run(this);
    }
}

Then you can call it in your main:

static void Main() {
    MyApplicationContext applicationContext = new MyApplicationContext();
    applicationContext.RunApplication();
}

I haven't tested this, but in theory it should work.

Edit 3: I realized there might be some thread safety issues here that you may have to work around as well. Check out the CodeProject article. It does it better than what I did here.

rakuo15 2010-07-09 21:00:09

I have a complex form and just instantiating it can take 1-2 seconds. I need a splash screen that displays immediately. I have seen various online articles about displaying Splash screens prior to calling Application.Run(). Thus, I am very interested to know if it is in fact required to call Application.Run() first.

Elan 2010-07-09 21:05:50

I've searched as well, and though I found [this article](http://msdn.microsoft.com/en-us/library/Aa446493), it doesn't quite do as you expect it to: it loads up the splash form in `Application.Run()` instead. What you do instead, if your form does a lot of processing, is call the splash form in the main form's constructor before any other call, that way it's the first thing that executes. Or you can use your `Application.Run()` on your splash screen and call the main form from there on a separate thread.

rakuo15 2010-07-09 21:12:28

I've added some stuff that I've found in [this article](http://www.codeproject.com/KB/cs/applicationcontextsplash.aspx) on CodeProject. Hopefully that gets you somewhere.

rakuo15 2010-07-09 21:25:21

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Why do I get "Object is currently in use elsewhere" exception?

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