working with UWP-EntryCellRenderer

I'm still beginner. At the moment I investigate EntryCellRenderer.

I managed Android.
There I have GetCellCore where I can build my UI (e.g. Spinner), add ItemSelected-Listener, ....
And I have OnCellPropertyChanged where I can update my UI.

I managed iOS.
There I have the GetCell function where I can build my UI (e.g. UIPickerView), add Done-Button for selecting value, ...

I'm stuck with UWP-EntryCellRenderer
I found only a GetTemplate function.

I managed adding some DataTemplate (with Combobox) as resource:

And I added
public override DataTemplate GetTemplate(Cell cell)
{
cell.PropertyChanged+=Cell_PropertyChanged;
return App.Current.Resources["MyTemplate"] as DataTemplate,
}

private void Cell_PropertyChanged(object Sender, EventArgs e)
{
}

But I don't know, where to add my code behind to initialize my ComboBox (add items programmatically, set initial index, ...) and how to update my UI after Cell_PropertyChanged occured.

Bye, Holger Gothan.