windows store app, bind to parent gridview property

Question

How to bind parent property from itemTemplate gridview ?

<GridView ItemsSource="{Binding UsersViewModel}" ItemTemplate="{StaticResource UsersTemplate}">            

<DataTemplate x:Key="UsersTemplate">        
        <ListView VerticalAlignment="Top" ItemsSource="{Binding Users}"
                  Height="{Binding Window.Current.Bounds.Height}"   
                  Width="{Binding PARENT?.ColWidth}"
                  ScrollViewer.VerticalScrollBarVisibility="Visible"                    
                  ItemTemplateSelector="{StaticResource UserTemplateSelector}"
                  ItemContainerStyle="{StaticResource LvItemStyle}" >
        </ListView>        
</DataTemplate>

ColWidth property is defined in UsersViewModel

Answer 1

Something about your Xaml code doesn't feel right, since you are binding your GridView's ItemSource to that UsersViewModel that feels like a property instead of a Collection ! (ItemSource should be bound to a collection). If UsersViewModel is indeed a Collection of a class objects that has in it the ColWidth property, then a simple binding inside the DataTemplate should do the trick,

Width="{Binding ColWidth}"

Now if UsersViewModel is meant to be the GridView's DataContext, then you code probably should look something like that,

<GridView DataContext="{Binding UsersViewModel}" ItemsSource="{Binding ACollectionInsideUsersViewModel}" ItemTemplate="{StaticResource UsersTemplate}">

In this case if the ColWidth property is defined inside the UsersViewModel object, then the easiest way to access the parent DataContext from a child is by using ElementName Binding :

 <GridView DataContext="{Binding UsersViewModel}" ItemsSource="{Binding ACollectionInsideUsersViewModel}" Name="gridView">
        <GridView.ItemTemplate>
            <DataTemplate >
                <ListView VerticalAlignment="Top" ItemsSource="{Binding Users}"
              Height="{Binding Window.Current.Bounds.Height}"   
              Width="{Binding DataContext.ColWidth,ElementName=gridView}"
              ScrollViewer.VerticalScrollBarVisibility="Visible"                    
              ItemTemplateSelector="{StaticResource UserTemplateSelector}"
              ItemContainerStyle="{StaticResource LvItemStyle}" >
                </ListView>
            </DataTemplate>
        </GridView.ItemTemplate>
    </GridView>