System.Windows.MessageBox doesn't wait for user input before going poof!

Question

...and it makes no sense why. T-T

In my Application_Startup event handler I have code that looks kinda like this:

private void Application_Startup(object sender, StartupEventArgs e)
{
    string errorMessage;

    if(CheckStartUpConditions(out errorMessage))
    {
        (new MainWindow()).Show();
    }
    else
    {
        MessageBox.Show(errorMessage, "Application Startup", 
            MessageBoxButton.OK, MessageBoxImage.Error);

        Shutdown();
    }
}

private bool CheckStartUpConditions(out string errorMessage)
{
    errorMessage = string.Empty;  

    if(...)
        errorMessage += "Please login to xxx. ";

    if(...)
        errorMessage += "Please install xxx.";

    if(string.IsNullOrEmpty(errorMessage))
        return true;
    else
        return false;
}

The message box makes an brief appearance for like a second before going "POOF!" It doesn't wait for me to click "OK" or on the "X" button. I'm really stumped as to why this is occuring, so any help would be greatly appreciated.

I've tried commenting out the call to Shutdown just for kicks and giggles, and it still behaves the same way.

Also, the application also has a SplashScreen, so I don't know if that's effecting this.

EDIT: I added more code if that helps. The message box is showing the correct error message. Just won't stay long enough for the users to read it. >:(

EDIT PART 2: Okay...I think I've found the culprit. :( I changed the build action on the image I'm using as my splash from SplashScreen to None and the message box will now stay and wait for user input. I don't understand why the SplashScreen is screwing with the MessageBox. >:(

Answer 1

The message box vanishes immediately because it has no owner. If you specify the option MessageBoxOptions.DefaultDesktopOnly, the desktop will be assigned as the owner, and the message box will work correctly on an application with no main window.

MessageBox.Show(
    "Message", 
    "Title",
    MessageBoxButton.YesNoCancel, 
    MessageBoxImage.Question, 
    MessageBoxResult.Cancel,
    MessageBoxOptions.DefaultDesktopOnly);