Why does WPF MenuItem IsChecked="True" triggers Checked Event during Initialization?

Question

Hi all.  Quick question here.  I have a MenuItem like this:

<MenuItem Header="Sound" IsCheckable="True" Checked="SoundOn" Unchecked="SoundOff" IsChecked="True" />

When the code behind initializes, it hits my SoundOn event handler because of IsChecked = true, and that prevents me from accessing elements in the window because they have not been initialized yet.  How do I prevent the initialization from triggering the event?

I am new to WPF so perhaps I am missing something obvious???

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Answer 1

You can check the IsInitialized property in the code behind. You may find you just need to add some simple checks as per below:

public partial class InitCallsEvents : Window
{
    private bool _isSoundOn = false;
    public InitCallsEvents()
    {
        InitializeComponent();
        //We are initialized now, check if any work needs to be done
        if (_isSoundOn)
        {
            TurnOnSound(); 
        }
    }
    private void SoundOn(object sender, RoutedEventArgs e)
    {
        Console.WriteLine("SoundOn({0}, {1}). IsInitialized={2}", sender, e, this.IsInitialized);
        _isSoundOn = true;
        if (this.IsInitialized)
        {
            TurnOnSound();
        }
    }
    private void SoundOff(object sender, RoutedEventArgs e)
    {
        Console.WriteLine("SoundOff({0}, {1}). IsInitialized={2}", sender, e, this.IsInitialized);
    }
    private void TurnOnSound()
    {
        Console.WriteLine("Turning sound on");
    }
}

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Lee Campbell http://LeeCampbell.blogspot.com

Answer 2

Hi smyrin,

You could register the Checked event after Initialization:

public MainWindow()
{
    InitializeComponent();
    menuItem.IsChecked = true;
    menuItem.Checked += new RoutedEventHandler(menuItem_Checked);
}

void menuItem_Checked(object sender, RoutedEventArgs e)
{
    //throw new NotImplementedException();
}

Best regards,

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Sheldon _Xiao
MSDN Community Support | Feedback to us
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Answer 3

Both answers are great examples of how to work around the issue.  Thanks!

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