Can I populate a Label within my CollectionView with a value outside the ItemsSource List that populates the view? - binding

Question

I have a Label within my CollectionView that I need to populate with a value outside the ItemsSource List that populates the view.
The following code is an example of what I am trying to accomplish but it seems that the CollectionView is limiting the binding context to just the Items list. I have tried naming the label and setting it in my c# code but I cant seem to access the label in c#. I suppose I could build the whole page in c# rather than using the .xaml but unlike this example my actual code uses multiple templates and a template selector. If I could figure this out without rewriting hours of code I would prefer it.
ItemsPage.xaml
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:d="http://xamarin.com/schemas/2014/forms/design"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d"
x:Class="TabTest.Views.ItemsPage"
Title="{Binding Title}"
x:Name="BrowseItemsPage">
<ContentPage.ToolbarItems>
<ToolbarItem Text="Add" Clicked="AddItem_Clicked" />
</ContentPage.ToolbarItems>
<StackLayout Padding="10">
<Label Text="{Binding TestVal}" FontSize="16" HeightRequest="20" />
<!-- ^^^^ This label displays just as expected -->
<RefreshView IsRefreshing="{Binding IsBusy, Mode=TwoWay}" Command="{Binding LoadItemsCommand}">
<CollectionView x:Name="ItemsCollectionView"
ItemsSource="{Binding Items}">
<CollectionView.ItemTemplate>
<DataTemplate>
<StackLayout Padding="10">
<Label x:Name="TestV" Text="{Binding Path=BindingContext.TestVal}" />
<!-- ^^^^ I want this Label to display the TestVal string in the ViewModel -->
<Label Text="{Binding Text}"
d:Text="{Binding .}"
LineBreakMode="NoWrap"
Style="{DynamicResource ListItemTextStyle}"
FontSize="16" />
<Label Text="{Binding Description}"
d:Text="Item descripton"
LineBreakMode="NoWrap"
Style="{DynamicResource ListItemDetailTextStyle}"
FontSize="13" />
<StackLayout.GestureRecognizers>
<TapGestureRecognizer NumberOfTapsRequired="1" Tapped="OnItemSelected"></TapGestureRecognizer>
</StackLayout.GestureRecognizers>
</StackLayout>
</DataTemplate>
</CollectionView.ItemTemplate>
</CollectionView>
</RefreshView>
</StackLayout>
</ContentPage>
ItemsViewModel.cs
namespace TabTest.ViewModels
{
public class ItemsViewModel : BaseViewModel
{
public ObservableCollection<Item> Items { get; set; }
public Command LoadItemsCommand { get; set; }
private string testVal;
public string TestVal // I want the value of this variable in that Label
{
get
{
return testVal;
}
set
{
testVal = value;
}
}
public ItemsViewModel()
{
Title = "Browse";
TestVal = "Value123";
Items = new ObservableCollection<Item>();
LoadItemsCommand = new Command(async () => await ExecuteLoadItemsCommand());
MessagingCenter.Subscribe<NewItemPage, Item>(this, "AddItem", async (obj, item) =>
{
var newItem = item as Item;
Items.Add(newItem);
await DataStore.AddItemAsync(newItem);
});
}
async Task ExecuteLoadItemsCommand()
{
IsBusy = true;
try
{
Items.Clear();
var items = await DataStore.GetItemsAsync(true);
foreach (var item in items)
{
Items.Add(item);
}
}
catch (Exception ex)
{
Debug.WriteLine(ex);
}
finally
{
IsBusy = false;
}
}
}
}

Answer 1

I ended up using a dynamic resource in Xaml and used code behind to modify the resource when it needed to change.
Xaml:
<Label x:Name="TestV" Text="{DynamicResource TestValue}" />
Code Behind:
Application.Current.Resources["TestValue"] = NewValue;
App.xaml:
<x:String x:Key="TestValue">Value123</x:String>