xamarin forms - two way binding with a picker - why cant I update a picker from code behind?

Question

My products page only shows \'Product Name\' and \'Quantity\', quantity isdisplayed/ binded to the picker.

For test purposes to get this working there is only 2 products

Answer 1

It looks like you have properly implemented INotifyPropertyChanged on your ProductModel, but now you need to subscribe to it in the constructor of the ProductModel class.

I have stubbed up a simple implementation of what it is that you are looking for (I excluded the rest of your code so that it would be easier to digest)

public class ProductModel : INotifyPropertyChanged {
        
        //Event
        public event PropertyChangedEventHandler PropertyChanged;

        //Fields
        private string _ProductName;
        private int _Quantity;

        //Properties
        public int Quantity {
            get { return _Quantity; }
            set {
                _Quantity = value;
                OnPropertyChanged();
            }
        }

        public string ProductName {
            get { return _ProductName; }
            set {
                _ProductName = value;
                OnPropertyChanged();
            }
        }


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

        //OnPropertyChanged
        private void OnPropertyChanged(object sender, PropertyChangedEventArgs e) {
            if (e.PropertyName == nameof(Quantity)) {
                //Do anything that needs doing when the Quantity changes here...
            }
        }

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

Let me know if this gets you going