Create table in SQLite with generic class 'Quantity' as a picker - ERROR not a valid type for SQLite DB

Question

Morning All,

xamarin forms - populate picker in MVVM from SQLite DB issue

So...Ive used the following post

https://www.c-sharpcorner.com/article/populate-picker-using-mvvm/
to help me include a populated picker using MVVM in my project, using a picker to allowing the user to select a 'Quantity' to order for each product (which all works fine as its populated from code, but now refactoring to load from SQLite..please see current code below)..

//ProductModel

     public class ProductModel : INotifyPropertyChanged
    {
        public event PropertyChangedEventHandler PropertyChanged;

        private int _ProductId;
        private string _BrandName;
        public ObservableCollection<Quantity> _ListQuantites;
        private Quantity _selectedQuantity;
//ETC have removed the other properties for sake of this Q


        //Constructor
        public ProductModel()
        {
            //Subscription
            this.PropertyChanged += OnPropertyChanged;
        }

        [PrimaryKey, AutoIncrement]
        public int ProductId
        {
            get { return _ProductId; }
            set
            {
                if (_ProductId == value) return;
                _ProductId = value;
                OnPropertyChanged();
            }
        }


        public ObservableCollection<Quantity> ListQuantites
        {
            get
            {
                return _ListQuantites;
            }
            set
            {
                _ListQuantites = value;
                OnPropertyChanged();
            }
        }

        public Quantity SelectedQuantity
        {
            get
            {
                return _selectedQuantity;
            }
            set
            {
                if (value == null)
                {
                    _selectedQuantity = _selectedQuantity;
                }
                else
                {
                    _selectedQuantity = value;
                    OnPropertyChanged();
                }
            }
        }


        //OnPropertyChanged
        private void OnPropertyChanged(object sender, PropertyChangedEventArgs e)
        {
            if (e.PropertyName == nameof(SelectedQuantity))
            {
                //test quantity amount
            }
        }

        // [NotifyPropertyChangedInvocator]
        protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
        {
            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
        }
    }

Up Until now I was populating the ProductModel with its picker, from the constructor of the ProductViewModel page with:

         WineList = new ObservableCollection<ProductModel>();
                    WineList.Add(new ProductModel { ProductId = 1, BrandName = "Mc guigans", Grape = "Red", ListQuantites = List_Quantites, Image = "W.png", Description = "Fruity Flav", Size="700ml", Price = 10.00M, SubTotalForItem = 0.00M, Genre = "Wine" });
    //etc...and so on

//then
 List_Quantites = PickerService.GetQuantitiesForProductPage();

//Picker service
     public static ObservableCollection<QuantityModel> GetQuantitiesForProductPage()
        {
            var quantities = new ObservableCollection<QuantityModel>()
            {
                new QuantityModel() {Key=1, Value="0"},
                new QuantityModel() {Key=2, Value="1"},
                new QuantityModel() {Key=3, Value="2"},
                new QuantityModel() {Key=4, Value="3"}
//etc
            };
            return quantities;
        }


//XAML

    <Picker Grid.Column="3" Grid.Row="0" Title="     " VerticalOptions="Center" x:Name="productPicker" VerticalTextAlignment="Center" HorizontalOptions="EndAndExpand"  ItemsSource="{Binding ListQuantites}" ItemDisplayBinding="{Binding Value}" SelectedIndexChanged="QuantityChanged" SelectedItem ="{Binding SelectedQuantity}"/>

So...yeah as I said all works fine and dandy...But now I would like to load the ProductModel list from a table in SQLite....I have already used SQLite basic CRUD operations to create, load, view, update, edit...etc for orders made...so this is also working...the problem I seem to be having is creating the table, it is failing when I try to create an entry in the table with 'Quantity'....obviously...so I have changed the code...change 'Quantity' to object, then the plan being to populate this on the VM...but this also didnt work...

found another post relating to this:

https://forums.xamarin.com/discussion/2546/create-table-in-xamarin-throws-exception-because-of-generic-list
So 'Quantity' class is not a valid type for SQLite DB value...but turns out neither is object...has anyone idea for a work around for this...or some advice on how to refactor to resolve this?

any help or point in the right direction is appreciated thank Y

UPDATE

 public class Quantity
    {
        public int Key { get; set; }
        public string Value { get; set; }
    }



//Create table
SQLiteConnection database;
 public ProductsDatabaseController()
        {
            database = DependencyService.Get<ISQLite>().GetConnection();
            SQLiteFunctionality SQLite = new SQLiteFunctionality(); 

database.CreateTable<ProductModel>();