在Xaml中绑定分组的Collection

Question

I've searched a bit, but the info I've found isn't what I need. So I decided to ask you all - I'm sure it's a newbie question but i really don't get it. Let's start: I have a DataSource which is a grouped observable collection. At the moment I've 2 groups with a different count of items. The two groups and the items belong to the same common base:

public DataCommon(String uniqueId, String title, String subtitle, String imagePath, String description)
    {
        this._uniqueId = uniqueId;
        this._title = title;
        this._subtitle = subtitle;
        this._description = description;
        this._imagePath = imagePath;
    }

This is the constructor of the model. In the ViewModel I fill it. Now I would like bind the ItemClick with a Command to my ViewModel. I do like this (only a short part):

<GridView
        x:Name="itemGridView"
        AutomationProperties.AutomationId="ItemGridView"
        AutomationProperties.Name="Grouped Items"
        Grid.RowSpan="2"
        Padding="116,137,40,46"
        ItemsSource="{Binding Source={StaticResource groupedItemsViewSource}}"
        ItemTemplate="{StaticResource Standard250x250ItemTemplate}"
        SelectionMode="None"
        IsSwipeEnabled="false"
        IsItemClickEnabled="True"
        >
        <WinRtBehaviors:Interaction.Behaviors>
            <Win8nl_Behavior:EventToCommandBehavior Event="ItemClick" Command="ItemClickCommand" CommandParameter="{Binding UniqueId}"/>
        </WinRtBehaviors:Interaction.Behaviors>

But now the problem. At the "Binding UniqueId" it's saying the DataContext is my ViewModel, so i can't connect it to the properties of the Model. Looked at the Page.DataContext i told XAML tu use my ViewModel as DataContext. I guess this was correct. But how can I access the Model-properties? I've tried to do it like this (defined my Model as DataModel):

<WinRtBehaviors:Interaction.Behaviors>
            <Win8nl_Behavior:EventToCommandBehavior Event="ItemClick" Command="ItemClickCommand" CommandParameter="{Binding DataModel:SampleDataCommon.UniqueId}"/>
        </WinRtBehaviors:Interaction.Behaviors>

but as I guessed beforehand it didn't work - as parameter i get null.

I would be thankful for any help, because as i said at the beginning of the post: I really don't get it...

Answer 1

You can't use EventToCommandBehavior in this way - this was also stated by its author in the comments .

I'm using the following attached property in such cases:

public static class ItemClickBehavior
{
    public static DependencyProperty ItemClickCommandProperty = DependencyProperty.RegisterAttached("ItemClickCommand",
                typeof(ICommand),
                typeof(ItemClickBehavior),
                new PropertyMetadata(null, OnItemClickCommandChanged));

    public static void SetItemClickCommand(DependencyObject target, ICommand value)
    {
        target.SetValue(ItemClickCommandProperty, value);
    }

    public static ICommand GetItemClickCommand(DependencyObject target) 
    {
        return (ICommand)target.GetValue(ItemClickCommandProperty);
    }

    private static void OnItemClickCommandChanged(DependencyObject target, DependencyPropertyChangedEventArgs e)
    {
        var element = target as ListViewBase;
        if (element != null)
        {
            // If we're putting in a new command and there wasn't one already
            // hook the event
            if ((e.NewValue != null) && (e.OldValue == null))
            {
                element.ItemClick += OnItemClick;
            }

            // If we're clearing the command and it wasn't already null
            // unhook the event
            else if ((e.NewValue == null) && (e.OldValue != null))
            {
                element.ItemClick -= OnItemClick;
            }
        }
    }

    static void OnItemClick(object sender, ItemClickEventArgs e)
    {
        GetItemClickCommand(sender as ListViewBase).Execute(e.ClickedItem);
    }
}

This is how you would bind a command to it:

<GridView
    x:Name="itemGridView"
    AutomationProperties.AutomationId="ItemGridView"
    AutomationProperties.Name="Grouped Items"
    Grid.RowSpan="2"
    Padding="116,137,40,46"
    ItemsSource="{Binding Source={StaticResource groupedItemsViewSource}}"
    ItemTemplate="{StaticResource Standard250x250ItemTemplate}"
    SelectionMode="None"
    IsSwipeEnabled="false"
    IsItemClickEnabled="True"
    itbmb:ItemClickBehavior.ItemClickCommand="{Binding ItemClickCommand}"
    >

I guess it wouldn't be all that difficult to create a behavior from the attached property if you really wanted to.