MenuItem.Checked Event

public event RoutedEventHandler Checked

/** @event */
public void add_Checked (RoutedEventHandler value)

/** @event */
public void remove_Checked (RoutedEventHandler value)

In JScript, you can handle the events defined by a class, but you cannot define your own.

<object Checked="RoutedEventHandler" .../>

<MenuItem Name="mi1" Style="{StaticResource CheckBoxMenu}" Header="Online"  
     Click="StatusClick" Checked="OnChecked" Unchecked="OnUnchecked"/>

private void OnChecked(object sender, RoutedEventArgs e)
{
    if (mi1.IsChecked == true)
    {
        textBlock1.Text = "Item is checked.";
    }
}