/// <summary>
/// Observe collection element's property.
/// </summary>
/// <typeparam name="TCollection">Type of collection</typeparam>
/// <typeparam name="TElement">Type of element</typeparam>
/// <typeparam name="TProperty">Type of property</typeparam>
/// <param name="source">Data source</param>
/// <param name="propertySelector">Property selection expression</param>
/// <param name="isPushCurrentValueAtFirst">Push current value on first subscribe</param>
/// <returns>Property value sequence</returns>
public static IObservable <PropertyPack <TElement, TProperty> > ObserveElementProperty <TCollection, TElement, TProperty>(TCollection source, Expression <Func <TElement, TProperty> > propertySelector, bool isPushCurrentValueAtFirst = true)
where TCollection : INotifyCollectionChanged, IEnumerable <TElement>
where TElement : class, INotifyPropertyChanged
{
if (source == null)
{
throw new ArgumentNullException(nameof(source));
}
if (propertySelector == null)
{
throw new ArgumentNullException(nameof(propertySelector));
}
var memberExpression = (MemberExpression)propertySelector.Body;
var propertyInfo = memberExpression.Member as PropertyInfo;
if (propertyInfo == null)
{
throw new ArgumentException($"{nameof(propertySelector)} is not property expression");
}
return(ObserveElementCore <TCollection, TElement, PropertyPack <TElement, TProperty> >
(
source,
(x, observer) => x.ObserveProperty(propertySelector, isPushCurrentValueAtFirst).Subscribe(y =>
{
var pair = PropertyPack.Create(x, propertyInfo, y);
observer.OnNext(pair);
})
));
}
/// <summary>
/// Observe collection element's IObservable sequence.
/// </summary>
/// <typeparam name="TCollection">Type of collection</typeparam>
/// <typeparam name="TElement">Type of collection element</typeparam>
/// <typeparam name="TProperty">Type of observable property element</typeparam>
/// <param name="source">Source collection</param>
/// <param name="propertySelector">IObservable selection expression</param>
/// <returns>IObservable sequence</returns>
public static IObservable <PropertyPack <TElement, TProperty> > ObserveElementObservableProperty <TCollection, TElement, TProperty>(TCollection source, Expression <Func <TElement, IObservable <TProperty> > > propertySelector)
where TCollection : INotifyCollectionChanged, IEnumerable <TElement>
where TElement : class
{
if (source == null)
{
throw new ArgumentNullException(nameof(source));
}
if (propertySelector == null)
{
throw new ArgumentNullException(nameof(propertySelector));
}
if (!(propertySelector.Body is MemberExpression memberExpression))
{
if (!(propertySelector.Body is UnaryExpression unaryExpression))
{
throw new ArgumentException(nameof(propertySelector));
}
var operand = unaryExpression.Operand as MemberExpression;
if (operand == null)
{
throw new ArgumentException(nameof(propertySelector));
}
memberExpression = operand;
}
var propertyInfo = memberExpression.Member as PropertyInfo;
if (propertyInfo == null)
{
throw new ArgumentException($"{nameof(propertySelector)} is not property expression");
}
// no use
var getter = AccessorCache <TElement> .LookupGet(propertySelector, out var propertyName);
return(ObserveElementCore <TCollection, TElement, PropertyPack <TElement, TProperty> >
(
source,
(x, observer) => getter(x).Subscribe(y =>
{
var pair = PropertyPack.Create(x, propertyInfo, y);
observer.OnNext(pair);
})
));
}