Implementing INotifyPropertyChanged with PostSharp 1.5
- by no9
Hello all.
Im new to .NET and WPF so i hope i will ask the question correctly.
I am using INotifyPropertyChanged implemented using PostSharp 1.5:
[Serializable, DebuggerNonUserCode, AttributeUsage(AttributeTargets.Assembly | AttributeTargets.Class, AllowMultiple = false, Inherited = false),
MulticastAttributeUsage(MulticastTargets.Class, AllowMultiple = false, Inheritance = MulticastInheritance.None, AllowExternalAssemblies = true)]
public sealed class NotifyPropertyChangedAttribute : CompoundAspect
{
public int AspectPriority { get; set; }
public override void ProvideAspects(object element, LaosReflectionAspectCollection collection)
{
Type targetType = (Type)element;
collection.AddAspect(targetType, new PropertyChangedAspect { AspectPriority = AspectPriority });
foreach (var info in targetType.GetProperties(BindingFlags.Public | BindingFlags.Instance).Where(pi => pi.GetSetMethod() != null))
{
collection.AddAspect(info.GetSetMethod(), new NotifyPropertyChangedAspect(info.Name) { AspectPriority = AspectPriority });
}
}
}
[Serializable]
internal sealed class PropertyChangedAspect : CompositionAspect
{
public override object CreateImplementationObject(InstanceBoundLaosEventArgs eventArgs)
{
return new PropertyChangedImpl(eventArgs.Instance);
}
public override Type GetPublicInterface(Type containerType)
{
return typeof(INotifyPropertyChanged);
}
public override CompositionAspectOptions GetOptions()
{
return CompositionAspectOptions.GenerateImplementationAccessor;
}
}
[Serializable]
internal sealed class NotifyPropertyChangedAspect : OnMethodBoundaryAspect
{
private readonly string _propertyName;
public NotifyPropertyChangedAspect(string propertyName)
{
if (string.IsNullOrEmpty(propertyName)) throw new ArgumentNullException("propertyName");
_propertyName = propertyName;
}
public override void OnEntry(MethodExecutionEventArgs eventArgs)
{
var targetType = eventArgs.Instance.GetType();
var setSetMethod = targetType.GetProperty(_propertyName);
if (setSetMethod == null) throw new AccessViolationException();
var oldValue = setSetMethod.GetValue(eventArgs.Instance, null);
var newValue = eventArgs.GetReadOnlyArgumentArray()[0];
if (oldValue == newValue) eventArgs.FlowBehavior = FlowBehavior.Return;
}
public override void OnSuccess(MethodExecutionEventArgs eventArgs)
{
var instance = eventArgs.Instance as IComposed<INotifyPropertyChanged>;
var imp = instance.GetImplementation(eventArgs.InstanceCredentials) as PropertyChangedImpl;
imp.OnPropertyChanged(_propertyName);
}
}
[Serializable]
internal sealed class PropertyChangedImpl : INotifyPropertyChanged
{
private readonly object _instance;
public PropertyChangedImpl(object instance)
{
if (instance == null) throw new ArgumentNullException("instance");
_instance = instance;
}
public event PropertyChangedEventHandler PropertyChanged;
internal void OnPropertyChanged(string propertyName)
{
if (string.IsNullOrEmpty(propertyName)) throw new ArgumentNullException("propertyName");
var handler = PropertyChanged as PropertyChangedEventHandler;
if (handler != null) handler(_instance, new PropertyChangedEventArgs(propertyName));
}
}
}
Then i have a couple of classes (user and adress) that implement [NotifyPropertyChanged].
It works fine. But what i want would be that if the child object changes (in my example address) that the parent object gets notified (in my case user). Would it be possible to expand this code so it automaticly creates listeners on parent objects that listen for changes in its child objets?
