带有导航的CallMethodAction导致多个导航调用

Question

I want to navigate to a new page when item is clicked in a ListView . I have following XAML (using Behaviors).

<ListView Grid.Row="1" ItemsSource="{Binding Subreddits}" Margin="-10,20,0,0" SelectionMode="None" IsItemClickEnabled="True">   
    <Interactivity:Interaction.Behaviors>
        <Core:EventTriggerBehavior EventName="ItemClick">
            <Core:CallMethodAction TargetObject="{Binding Mode=OneWay}" MethodName="SubredditTapped"/>
        </Core:EventTriggerBehavior>
    </Interactivity:Interaction.Behaviors>
</ListView>

I have enabled caching on my page as follows:

public MyPage1()
{
    this.InitializeComponent();
    NavigationCacheMode = NavigationCacheMode.Required;     
}

Here's my SubredditTapped method:

public void SubredditTapped(object sender, object parameter)
{
    var args = parameter as Windows.UI.Xaml.Controls.ItemClickEventArgs;
    var clickedItem = args.ClickedItem as Subreddit;
    string navigationParamName = "Subreddit";
    BootStrapper.Current.SessionState[navigationParamName] = clickedItem;
    BootStrapper.Current.NavigationService.Navigate(typeof(MyPage2), navigationParamName);
    return;           
}

Now, when I tap an item for the first time, frame navigates to MyPage2 as expected. When I navigate back to MyPage1 (using back button) and then again navigate to MyPage2 (by tapping an item) the SubredditTapped method is called twice. This number goes on increasing as I navigate back and forth.
Since disabling cache on MyPage1 gets rid of this problem, I suspect that the method SubredditTapped is added to delegate list of ItemClick every time MyPage1 is navigated to. How do I prevent this from happening? What is the correct way to do this without breaking MVVM?

Edit: The bug in Behaviours SDK has been fixed in newer versions. So this works.

Answer 1

On the ViewModel the has the Subreddits, create a property of the Subreddit type for the SelectedSubreddit, and bind SelectedItem of the ListBox to this new property with a 2way binding. Then in the setter of the new property ( which will get called when a list item is selected ) you can call the method there.