更改模型值时更新可观察的集合

Question

我正在为我的食谱应用程序编写一个成分计算器，该计算器从选择器中获取一个值，并将ObservableCollection中的成分数量更改为用户选择的人数。调试表明，后面的代码可以正常工作，但是可观察的集合不会用新值更新UI。请帮忙。

namespace SQLiteListView.Models
{
    public class Ingredients : INotifyPropertyChanged
    {
        // primary key
        [PrimaryKey, AutoIncrement]
        public int IngredientsId { get; set; }

        // other attributes
        private string _ingredientsName { get; set; }
        private double _ammount { get; set; }
        private string _units { get; set; }

        public string IngredientsName
        {
            get { return _ingredientsName; }
            set
            {
                _ingredientsName = value;
                OnPropertyChange("IngredientsName");
            }
        }
        public double Ammount
        {
            get { return _ammount; }
            set
            {
                _ammount = value;
                OnPropertyChange("ammount");
            }
        }
        public string Units
        {
            get { return _units; }
            set
            {
                _units = value;
                OnPropertyChange("Units");
            }
        }
        public int RecipeID
        {
            get { return _recipeID; }
            set
            {
                _recipeID = value;
                OnPropertyChange("RecipeID");
            }
        }

        // specify the foreign key
        [ForeignKey(typeof(Recipe))]
        public int _recipeID { get; set; }

        // many to one relationship with recipe
        [ManyToOne]
        public Recipe Recipe { get; set; }

        public event PropertyChangedEventHandler PropertyChanged;

        private void OnPropertyChange(string propertyName)
        {
            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
        }
    }

}

ViewModel

private PickerNo _selectedPicker { get; set; }

public PickerNo SelectedPicker
{
    get { return _selectedPicker; }
    set
    {
        _selectedPicker = value;
        IngredientsCalculator();
    }
}

   void IngredientsCalculator()
{
    var ingredients = new ObservableCollection<Ingredients>();
    foreach (Ingredients i in IngredientsList)
    {
        i.Ammount = (i.Ammount / Recipe.Serves) * SelectedPicker.NumberOfPeople;
        OnPropertyChanged();
    }
}
public event PropertyChangedEventHandler PropertyChanged;

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