BB84.Notifications 1.5.0

BB84.Notifications

Contains relevant things for property one-way binding / two-way binding, for property change / changing notification and for collection change / changing notification.

Usage

Depending on the application, there are several ways to skin a cat.

The bindable property class and interfaces

Designed with one or two way binding in mind.

public IBindableProperty<int> BindableInt { get; set; } = new BindableProperty<int>(default);

If the property is changed, the BindablePropertyChangingEventHandler<T> is triggered before the value changes and the BindablePropertyChangedEventHandler<T> is triggered after the value has changed.

• The BindablePropertyChangingEventHandler<T> contains via the BindablePropertyChangingEventArgs the old value.
• The BindablePropertyChangedEventHandler<T> contains via the BindablePropertyChangedEventArgs the new value.

Further implementation possibilities can be achieved with the help of the IBindableProperty interface.

The notification property base class and interfaces

Designed to handle changes at the class level and propagate them forward to the outside.

public sealed class TestClass : NotifyPropertyBase
{
    private int _property;

    public int Property
    {
        get => _property;
        set => SetProperty(ref _property, value);
    }
}

If the property is changed, the PropertyChangingEventHandler is triggered before the value changes and the PropertyChangedEventHandler is triggered after the value has changed.

• The PropertyChangingEventHandler contains via the CollectionChangingEventArgs the name of the property that is changing and the old value.
• The PropertyChangedEventHandler contains via the PropertyChangedEventArgs the name of the property that has changed and the new value.

Further implementation possibilities can be achieved using the INotifyPropertyChanged and INotifyPropertyChanging interfaces.

The notification collection base class and interfaces

The NotifyCollectionBase class provides methods to handle the change within a collection and propagate it to the outside.

public sealed class MyStringCollection : NotifyCollectionBase, ICollection<string>
{
  private readonly Collection<string> _collection;

  public MyStringCollection()
    => _collection = new Collection<string>();

  ..
}

Most of the implementation must be done despite the base class itself. The intention has been to be able to signal the state of a collection before (CollectionChangingEventHandler) or after (CollectionChangedEventHandler) the addition, deletion or modification of objects.

• The CollectionChangingEventHandler contains via the CollectionChangingEventArgs the CollectionChangeAction and can contain the object before the change depending on the action.
• The CollectionChangedEventHandler contains via the CollectionChangedEventArgs the CollectionChangeAction and can contain the object after the change depending on the action.

Further implementation possibilities can be achieved with the interfaces INotifyCollectionChanged and INotifyCollectionChanging.

The notification attributes

The NotifyChangedAttribute and the NotifyChangingAttribute propagating the information also to those properties the are defined via the constructor. An example implementation could look like this:

private sealed class TestClass : NotifyPropertyBase
{
  private int _quantity;
  private int _value;

  public TestClass(int quantity, int value)
  {
    Quantity = quantity;
    Value = value;
  }

  [NotifyChanged(nameof(TotalValue))]
  public int Quantity { get => _quantity; set => SetProperty(ref _quantity, value); }

  [NotifyChanged(nameof(TotalValue))]
  public int Value { get => _value; set => SetProperty(ref _value, value); }

  public int TotalValue => Quantity * Value;
}

If the Quantity property or the Value property is changed, a PropertyChanged event is also triggered for the TotalValue property.

Documentation

The API documentation can be found here.