public static ViewModelPropertyObserver <T> GetPropertyObserver <T>(this INotifyPropertyChanged notifyPropertyChanged, string propertyName)
{
ViewModelPropertyObserver <T> observer = new ViewModelPropertyObserver <T>();
var property = notifyPropertyChanged.GetType().GetProperty(propertyName);
if (property == null)
{
throw new Exception("Can not obeserve property");
}
notifyPropertyChanged.PropertyChanged += (s, args) =>
{
if (s != notifyPropertyChanged)
{
return;
}
if (args.PropertyName != propertyName)
{
return;
}
observer.PropertyValue = (T)property.GetValue(s, null);
observer.NumberOfTimesPropertyChanged++;
};
observer.PropertyValue = (T)property.GetValue(notifyPropertyChanged, null);
return(observer);
}
public static void AssertProperyHasChanged <T>(this ViewModelPropertyObserver <T> observer, T t)
{
Assert.AreEqual(t, observer.PropertyValue);
Assert.AreNotEqual(0, observer.NumberOfTimesPropertyChanged);
}