/// <summary>
/// Converts target property's ErrorsChanged to an observable sequence.
/// </summary>
/// <param name="propertySelector">Argument is self, Return is target property.</param>
public static IObservable <TProperty> ObserveErrorInfo <TSubject, TProperty>(
this TSubject subject, Expression <Func <TSubject, TProperty> > propertySelector)
where TSubject : INotifyDataErrorInfo
{
string propertyName;
var accessor = AccessorCache <TSubject> .LookupGet(propertySelector, out propertyName);
var result = subject.ErrorsChangedAsObservable()
.Where(e => e.PropertyName == propertyName)
.Select(_ => ((Func <TSubject, TProperty>)accessor).Invoke(subject));
return(result);
}
/// <summary>
/// Converts NotificationObject's property changed to an observable sequence.
/// </summary>
/// <param name="propertySelector">Argument is self, Return is target property.</param>
/// <param name="isPushCurrentValueOnSubscribe">Push current value on first subscribe.</param>
public static IObservable <TProperty> ObserveProperty <TSubject, TProperty>(
this TSubject subject, Expression <Func <TSubject, TProperty> > propertySelector,
bool isPushCurrentValueAtFirst = true)
where TSubject : INotifyPropertyChanged
{
string propertyName;
var accessor = AccessorCache <TSubject> .LookupGet(propertySelector, out propertyName);
var isFirst = true;
var result = Observable.Defer(() =>
{
var flag = isFirst;
isFirst = false;
var q = subject.PropertyChangedAsObservable()
.Where(e => e.PropertyName == propertyName)
.Select(_ => accessor.Invoke(subject));
return((isPushCurrentValueAtFirst && flag) ? q.StartWith(accessor.Invoke(subject)) : q);
});
return(result);
}
