private static IDisposable WhenChanged <TProperty>(LambdaExpression propertyToListen, Action <TProperty> listener, object source)
{
var sp = ExpressionHelper.GetSourceAndPropertyName <object, TProperty>(source, propertyToListen);
if (sp.Source is INotifyPropertyChanged npc)
{
var propertyName = sp.PropertyName;
var disposable = EventBindingHandler <PropertyChangedEventHandler> .Create(
(_, e) =>
{
if (propertyName.Equals(e.PropertyName))
{
if (npc.CanRead(e.PropertyName))
{
listener?.Invoke((TProperty)npc.Read(e.PropertyName));
}
}
},
x => npc.PropertyChanged += x,
x => npc.PropertyChanged -= x);
return(disposable);
}
return(null);
}
public void ObserverProperty_Test2()
{
var c1 = new Counter();
int ctr = 0;
var ev = EventBindingHandler <PropertyChangedEventHandler>
.Create(c1, "PropertyChanged", (_, e) =>
{
ctr++;
});
c1.Count++;
ev.Dispose();
Assert.AreEqual(1, ctr);
}