Window Loaded and WPF

Question

I have a WPF project in Windows 2012 in which I need to load some information in the Window Loaded event. I need to do this in the View Model rather than in the CodeBehind, though. I am attempting to use the following code:

In my xaml:

<interactivity:Interaction.Behaviors>
    <behaviors:WindowLoadedBehavior LoadedCommand="{Binding WindowLoadedCommand}" />
</interactivity:Interaction.Behaviors>

In my View Model:

private DelegateCommand _WindowLoadedCommand;

public DelegateCommand WindowLoadedCommand
{
    get
    {
        return _WindowLoadedCommand;
    }
    private set
    {
        _WindowLoadedCommand = value;
    }
}

public ShellViewModel()
{
    WindowLoadedCommand = new DelegateCommand(WindowLoadedAction);
}

protected void WindowLoadedAction()
{
    ...
}

My attached behavior:

public class WindowLoadedBehavior : Behavior<FrameworkElement>
{
    [SuppressMessage("Microsoft.StyleCop.CSharp.MaintainabilityRules", "SA1401:FieldsMustBePrivate", Justification = "Dependency Property.  Allow public.")]
    public static DependencyProperty LoadedCommandProperty = DependencyProperty.Register("LoadedCommand", typeof(ICommand), typeof(WindowLoadedBehavior), new PropertyMetadata(null));

    public ICommand LoadedCommand
    {
        get { return (ICommand)GetValue(LoadedCommandProperty); }
        set { SetValue(LoadedCommandProperty, value); }
    }

    protected override void OnAttached()
    {
        base.OnAttached();

        AssociatedObject.Loaded += AssociatedObject_Loaded;
    }

    protected override void OnDetaching()
    {
        AssociatedObject.Loaded -= AssociatedObject_Loaded;

        base.OnDetaching();
    }

    private void AssociatedObject_Loaded(object sender, RoutedEventArgs e)
    {
        if (LoadedCommand != null)
            LoadedCommand.Execute(null);
    }
}

The OnAttached, AssociatedObject_Loaded and LoadedCommand get are all firing, but the LoadedCommand set is not firing and, obviously, the WindowLoadedCommand isn't firing. Any clue what I can do to get this working?

Any particular reason you aren't binding to the command directly? — Bob., Sep 25 '12 at 19:38
From what I've read, binding the Window Loaded event directly doesn't work for some reason. — Dirk Dastardly, Sep 26 '12 at 11:34

score 37 · Accepted Answer · edited May 23 '17 at 11:46

37

There are a few options. A couple of them listed here:

how to call a window's Loaded event in WPF MVVM?

However, in the off chance that you or anyone else cares that you are spending several hours to complete a task that should have taken 30 seconds, you might want to try this instead.

public MainWindow()
{
    InitializeComponent();

    this.Loaded += new RoutedEventHandler(MainWindow_Loaded);
}

void MainWindow_Loaded(object sender, RoutedEventArgs e)
{
    ShellViewModel.Instance.WindowLoadedCommand.Execute(null);
}

edited May 23 '17 at 11:46

Community

1
1

answered Sep 25 '12 at 21:19

Harlow Burgess

1,876
14
12

2

That was perfect! Apparently the problem I was running into is that the event handling classes were not loaded properly before the window was loading. Your method (along with being short and to the point) avoided that and allowed it to fire correctly. – Dirk Dastardly Sep 26 '12 at 12:50

Window Loaded and WPF

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