Xamarin Forms with UWP Refresh causes value to disappear - xaml

Question

I have a Xamarin Forms application using Android and UWP. Everything works fine under Android but under UWP I have a problem when I want to modify some values displayed on the screen.
Here is my (simplified) ViewModel (using Fody.PropertyChanged) :
public class SalesViewModel : BaseAppViewModel
{
public ObservableCollection<SaleModel> Sales { get; set; }
= new ObservableCollection<SaleModel>();
[DoNotNotify]
public ICommand AddQuantityCommand => new Command<SaleModel>(item =>
{
item.Quantity += 1;
});
}
The BaseAppViewModel implement the INotifyPropertyChanged interface for Fody.PropertyChanged
The (simplified) SaleModel class:
public class SaleModel : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
public double Quantity { get; set; }
}
And the (part of the) XAML which display the list of SaleModel's
<ListView x:Name="ListView" ItemsSource="{Binding Sales, Mode=TwoWay}" SelectedItem="{Binding SelectedSale, Mode=TwoWay}">
<ListView.ItemTemplate>
<DataTemplate>
<ViewCell>
<ViewCell.View>
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*" />
<ColumnDefinition Width="*" />
</Grid.ColumnDefinitions>
<Image Grid.Column="0" Source="arrow.png">
<Image.GestureRecognizers>
<TapGestureRecognizer Command="{Binding Path=BindingContext.AddQuantityCommand, Source={x:Reference Name=SalesPage}}" CommandParameter="{Binding .}" />
</Image.GestureRecognizers>
</Image>
<Label Grid.Column="1" Text="{Binding Quantity, Mode=OneWay}"
</Grid>
</ViewCell.View>
</ViewCell>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
When clicking on the Image, the quantity is incremented but the value disappear from the screen under UWP.

Answer 1

I have tested your code and reproduced your issue. And I written the following ViewCell replace yours. Please try to modify your ViewCell.
<ViewCell>
<StackLayout BackgroundColor="#eee"
Orientation="Vertical">
<StackLayout Orientation="Horizontal">
<Image Source="time.jpg" HeightRequest="50" WidthRequest="50" >
<Image.GestureRecognizers>
<TapGestureRecognizer Command="{Binding AddQuantityCommand} " CommandParameter="{Binding .}"/>
</Image.GestureRecognizers>
</Image>
<Label Text="{Binding Quantity}"
TextColor="#f35e20" />
<Label Text="{Binding Quantity}"
HorizontalOptions="EndAndExpand"
TextColor="#503026" />
</StackLayout>
</StackLayout>
</ViewCell>
I have upload code sample to github. Please refer to.