MessageBox.Show on Form_Load?

Question

MessageBox.Show on Form_Load?

Peter Volz 1,295

Hello

My question is about .net framework 4.0 WinForms apps.

Is displaying a MessageBox.Show on main form's Load event bad?

Can cause any problems in exceptional cases?

2 conditions I use it are if min os req is not met a message box is shown to notify and then end the app

or if some less serious conditions are not met show a message box (question) and ask use to continue or end the app?

Because sometimes I get such remote reports:

System.InvalidOperationException: Showing a modal dialog box or form when the application is not running in UserInteractive mode is not a valid operation. Specify the ServiceNotification or DefaultDesktopOnly style to display a notification from a service application.
at System.Windows.Forms.Form.ShowDialog(IWin32Window owner)
at MessageBox...

David Lowndes 2,640 Reputation points MVP

2023-09-25T21:43:04.09+00:00

Are those reports because someone is trying to run your GUI application as a service?
RLWA32 49,536 Reputation points

2023-09-25T23:16:27.3866667+00:00

Maybe the application is being started by the task scheduler or some other non-interactive process?
Peter Volz 1,295 Reputation points

2023-09-25T23:32:49.39+00:00

Thanks all, I don't know how they tried to run it.

I didn't know if a GUI app can be run as service, but if being started by the task scheduler, how should I handle the situation?
KOZ6.0 6,655 Reputation points

2023-09-25T23:49:12.2366667+00:00

I like to do it before creating an instance of Form.

Display in Main()
Peter Volz 1,295 Reputation points

2023-09-26T02:06:06.2566667+00:00

VB.net project, Enable Application Framework = Checked :(

No main()

Any advise plz?

Accepted answer

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Your answer

David Lowndes 2,640 Reputation points MVP

2023-09-25T21:43:04.09+00:00

Are those reports because someone is trying to run your GUI application as a service?
RLWA32 49,536 Reputation points

2023-09-25T23:16:27.3866667+00:00

Maybe the application is being started by the task scheduler or some other non-interactive process?
Peter Volz 1,295 Reputation points

2023-09-25T23:32:49.39+00:00

Thanks all, I don't know how they tried to run it.

I didn't know if a GUI app can be run as service, but if being started by the task scheduler, how should I handle the situation?
KOZ6.0 6,655 Reputation points

2023-09-25T23:49:12.2366667+00:00

I like to do it before creating an instance of Form.

Display in Main()
Peter Volz 1,295 Reputation points

2023-09-26T02:06:06.2566667+00:00

VB.net project, Enable Application Framework = Checked :(

No main()

Any advise plz?

Answer 1

RLWA32 49,536

If the real issue is that your application is running in a non-interactive environment then moving the message box from the Load event to the Startup event will not solve your problem.

In the Startup event you should check the Environment.UserInteractive Property. If it is false then you cannot display a message box or a Form successfully. You should use an alternate method to provide user feedback such as writing to the Application Event log and/or to a file.

Peter Volz 1,295 Reputation points

2023-09-26T20:01:54.8466667+00:00

Thank you so much, you really saved me, just one thing, for minimum app requirements check like os version and installed .net framework version etc, is better to check in Startup event or main form_Load event?

And in such case if Environment.UserInteractive = False, should I just not use the MessageBox or terminate the whole app? Since my app is GUI only!
Peter Volz 1,295 Reputation points

2023-09-26T20:32:19.2633333+00:00

And in such case if Environment.UserInteractive = False, should I just not show MessageBox or terminate the whole app? Cause my app is GUI only!
RLWA32 49,536 Reputation points

2023-09-26T21:00:35.48+00:00

Presumably you could do whatever checking you desire but if the app is running in a non-interactive environment you should provide feedback to the user without using a message box or a form and then terminate it. It seems to me that the Startup event is a good place to do this stuff.
Peter Volz 1,295 Reputation points

2023-09-26T21:08:08.6233333+00:00

Thanks indeed :)
RLWA32 49,536 Reputation points

2023-09-26T21:10:48.8566667+00:00

You're welcome. You can test your implementation of the solution by creating a scheduled task to run your application and configuring the task to run whether or not the user is logged on. That will cause the task to run in a non-interactive environment.

Answer 2

Jiachen Li-MSFT 34,221 Microsoft External Staff

Hi @Peter Volz ,

Click View Application Events in project properties.

Then handle the startup event.

    Partial Friend Class MyApplication
        Private Sub a() Handles Me.Startup
            MessageBox.Show("Startup")
        End Sub
    End Class

Best Regards.

Jiachen Li

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MessageBox.Show on Form_Load?

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