Show CollectionView Grouping not working in Xamarin - xamarin.forms

Question

I have an article here about showing Data Groups from Preferences . As per everyone's input I switched to CollectionView. I have consulted the article https://learn.microsoft.com/en-us/xamarin/xamarin-forms/user-interface/collectionview/grouping. This is what I have:
public class CartUser
{
public int IDProduct { get; set; }
public string NameProduct { get; set; }
public string SupplierID { get; set; }
}
SupplierIDGrouping.cs
public class SupplierIDGrouping : ObservableCollection<CartUser>
{
public string SupplierID { get; private set; }
public SupplierIDGrouping(string supplierID)
: base()
{
SupplierID = supplierID;
}
public SupplierIDGrouping(string supplierID, IEnumerable<CartUser> source)
: base(source)
{
SupplierID = supplierID;
}
}
PageOne.xaml
<CollectionView ItemsSource="{Binding SupplierList}" IsGrouped="true">
<CollectionView.ItemTemplate>
<DataTemplate>
<Label Text="{Binding NameProduct}"/>
</DataTemplate>
</CollectionView.ItemTemplate>
</CollectionView>
PageOne.xaml.cs
public ObservableCollection<SupplierIDGrouping> SupplierList { get; private set; } = new ObservableCollection<SupplierIDGrouping>();
List<CartUser> cartUsers = new List<CartUser>();
var mycart = Preferences.Get("CartUserAdds", "_mycart");
var getcart = JsonConvert.DeserializeObject<List<CartUser>>(mycart);
cartUsers = getcart;
foreach (var item in cartUsers)
{
if (!SupplierList.Any(supplierid => supplierid.SupplierID == item.SupplierID))
{
SupplierList.Add(new SupplierIDGrouping(item.SupplierID));
}
SupplierList.Single(supplierid => supplierid.SupplierID== item.SupplierID).Add(item);
}
BindingContext = this;
The data I am taken from Preferences:
[{\"IDProduct\":1,\"NameProduct\":\"Name product 1\",\"SupplierID\":\"22379356\"},{\"IDProduct\":2,\"NameProduct\":\"Name product 2\",\"SupplierID\":\"22379356\"},{\"IDProduct\":3,\"NameProduct\":\"Name product 3\",\"SupplierID\":\"12336544\"}]
However my results are still not grouped by SupplierID
This is what I want:
Looking forward to everyone's help. Thank you very much!
Update
Data corresponds to 2 groups. Group 1: 2 products, group 2: 1 product
foreach (var item in cartUsers)
{
if (!SupplierList.Any(supplierid => supplierid.SupplierID == item.SupplierID))
{
SupplierList.Add(new SupplierIDGrouping(item.SupplierID));
}
SupplierList.Single(supplierid => supplierid.SupplierID== item.SupplierID).Add(item);
}
var getresult = SupplierList;
foreach(var i in getresult)
{
}
BindingContext = this;
Update 2
public class SupplierIDGrouping : ObservableCollection<CartUser>
{
public string SupplierID { get; private set; }
public string Name { get { return SupplierID; } }
public SupplierIDGrouping(string supplierID)
: base()
{
SupplierID = supplierID;
}
public SupplierIDGrouping(string supplierID, IEnumerable<CartUser> source)
: base(source)
{
SupplierID = supplierID;
}
}
PageOne.xaml
<CollectionView ItemsSource="{Binding SupplierList}" IsGrouped="true" Header="{Binding Name}">
<CollectionView.ItemTemplate>
<DataTemplate>
<Label Text="{Binding NameProduct}"/>
</DataTemplate>
</CollectionView.ItemTemplate>
</CollectionView>

Answer 1

I had to provide a GroupHeaderTemplate to make it work. Not sure why - according to the docs it should not be necessary
<CollectionView.GroupHeaderTemplate>
<DataTemplate>
<Label Text="{Binding SupplierID}"
BackgroundColor="LightGray"
FontSize="Large"
FontAttributes="Bold" />
</DataTemplate>
</CollectionView.GroupHeaderTemplate>