Bind a grouped Collection in Xaml - xaml

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.