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vb.netsplash-screen

Splash-screen threading error due to startup form closing

I have a splash-screen for a desktop app that I am making. The way the startup works is that it checks for certain files, if it finds them it closes immediately and loads up the main form.

However by doing so I get a threading error. I'm guessing its because the startup form closes before fully loading the Main form.

Here's the error message:

Cross-thread operation not valid: Control 'frm_SplashScreen' accessed from a thread other than the thread it was created on.

I've tried putting the thread to sleep, and even using timers to give the form time to load. But so far unsuccessfully.

Private Sub frm_Load_Load(sender As Object, e As EventArgs) Handles MyBase.Load
If Dir("System.dll") = "" then
 Createfile()
 Frm_Main.show()
 Me.close()
Else  
 Frm_Main.show()
 Me.close()
End IF

Everything else regarding the splash-screen is done in the project properties under application. Otherwise it is just an empty form.

How can I fix this?

Solution

  • In WinForms, the splash screen is not responsible for creating the main form and should not do so. If you have code that needs to run before the main form is created, while the splash screen is visible, place that code in the application's Startup event. Here's how to do it:

    1. Go to the application tab of your project's properties (same place you set the startup form and splash screen).
    2. Click on "View Application Events"
    3. In the event dropdown near the top of the window, select "Startup". This should create an event handler method for the Startup event, if it doesn't already exist (Private Sub MyApplication_Startup(sender, e) Handles Me.Startup).
    4. Put your code (the If Dir(...) Then Createfile() stuff in your example code) in the event handler.

    The code in the Startup event handler will be called before the main form is created. The splash screen will automatically be created, displayed, and destroyed in another thread. You don't need to worry about creating or closing the splash screen, as that is done automatically.

    If your startup code determines that you don't want the main form to be displayed at all, set e.Cancel = true in the startup event handler method and the application will quit instead of bringing up the main form.