EntityAspect.PropertyChanged, Event bubbling and Dirtying Parent objects.

   This is a little bit weird.  We have added a PropertyChanged handler to our base child entity so it can bubble events up to its parent object and bubble events for readonly properties.  

Please bear with me.  First I will explain why I need this foolishness.  Second, I will show the code.  Third, I will ask my question.

I have two example requirements:

A) When any OrderDetail changes, the UI should refresh the OrderTotal; and

B) When any part of an Order or OrderDetail changes, the Order and the changed Order Details should be saved as a set.

For A), When a user changes an OrderDetail:BaseChildEntity in the Order:BaseEntity, the readonly Order.OrderTotal property needs to fire a PropertyChanged("OrderTotal") event so the UI control that is bound to it will refresh.  In order to do this, I am capturing the Entity.EntityAspect.IsChanged property change in the child entity and bubbling it up from the EntityAspect to the parent.

For B), When a user changes an OrderDetail:BaseChildEntity in the Order:BaseEntity, the Order should be marked as dirty (i.e. Order.EntityAspect.IsChanged) so that when saved, the Entity Manager will save the Order and the changed Order Details.

To accomplish this, I have coded the following:

1) In BaseEntity, which Order derives from:

public abstract class BaseEntity : Entity

{

     protected BaseEntity()

     {

          base.EntityAspect.PropertyChanged += EntityAspectPropertyChanged; // This is probably NOT the right place to do this, but until we can find something better, this seems to work.  Suggestions?

     }

     private void EntityAspectPropertyChanged(object sender, PropertyChangedEventArgs e)

     {

          this.EntityAspectPropertyChangedInternal(sender, e);

     }

     protected virtual void EntityAspectPropertyChangedInternal(object sender, PropertyChangedEventArgs e)

     {

          if (e.PropertyName == "IsChanged") //take the Entity.EntityAspect.IsChanged property change

          {

               RaisePropertyChanged("IsChanged"); //and turn it into an Entity.IsChanged property change

          }

     }

}

2) In BaseChildEntity, which OrderDetail derives from:

public abstract class BaseChildEntity : BaseEntity

{

     protected abstract BaseEntity Parent { get; set; } 

     protected override void EntityAspectPropertyChangedInternal(object sender, System.ComponentModel.PropertyChangedEventArgs e)

     {     

          base.EntityPropertyChangedInternal(sender, e);

          if (e.PropertyName == "IsChanged" && this.EntityAspect.IsChanged)

          {

               //entity just got dirtied, so dirty the parent too

               this.Parent.EntityAspect.SetModified();

          }

     }

}

3) In OrderDetail:

public partial class OrderDetail

{

     protected override BaseEntity Parent

     {

          get

          {

               return Order; //Expose the RelatedEntity>Order as this OrderDetail's Parent

          }

          set

          {

               Order = value as Order;

          }

     }

}

4) In Order:

public partial class Order

{

     public double OrderTotal()

     {

          return Sum(this.OrderDetails);

     }

     private void OrderDetailPropertyChanged(object sender, PropertyChangedEventArgs e) //there is a horrible amount of code in this class that handles ensuring that this event handler is tied to each OrderDetail.PropertyChanged event.

     {

          this.RaisePropertyChanged("OrderTotal");

     }

}

OK.  So here's what I expect to happen:  

For requirement A) When an OrderDetail is edited, the OrderDetail.EntityAspect.IsChanged property gets changed, which is caught in BaseEntity.EntityAspectPropertyChanged, which then raises the OrderDetail.IsChanged property changed event, which is caught by the Order.OrderDetailPropertyChanged event handler, which then raises the Order.OrderTotal property changed event, which tells the UI bound to Order.OrderTotal to refresh.

For requirement B) When an OrderDetail is edited, the EntityAspect.IsChanged property gets changed, which is caught in BaseEntity.EntityAspectPropertyChanged, which then delegates to the BaseChildEntity.EntityAspectPropertyChangedInternal, which calls SetModified() on the parent Order.  Now, when the Order is saved, the EM will save the Order and the changed OrderDetails all at once.  When the Em.SaveChangesAsync is called, I expect all items to be saved and reset to EntityState = NotModified and IsChanged = false.

But, of course, it didn't work out that way.

First, is this just ridiculous?  Am I doing something silly to accomplish what I need?  My actual problem is messier and more complicated than this, so I would love to hear someone say this is not insane.

Second, when the EntityManager.SaveChangesAsync processes, the BaseEntity.EntityAspectPropertyChanged is called twice.  Once for the EntityAspect.EntityState property, and once for the EntityAspect.IsChanged property.  I assumed this was firing when these items are being reset after the save/replace process, but when the OrderDetail calls these, the test in the BaseChildEntity.EntityAspectPropertyChangedInternal > if (e.PropertyName == "IsChanged" && this.EntityAspect.IsChanged) still returns true.  Why?  What am I doing wrong?  How can I accomplish what I need?

Here's the call stack at that moment:

Model.DomainModel!DomainModel.BaseChildEntity.EntityAspectPropertyChangedInternal(object sender = {IdeaBlade.EntityModel.EntityAspect}, System.ComponentModel.PropertyChangedEventArgs e = {System.ComponentModel.PropertyChangedEventArgs}) Line 39     C#

>     Png.GcsAg.Model.DomainModel!Png.GcsAg.Model.DomainModel.BaseEntity.EntityAspect_PropertyChanged(object sender = {IdeaBlade.EntityModel.EntityAspect}, System.ComponentModel.PropertyChangedEventArgs e = {System.ComponentModel.PropertyChangedEventArgs}) Line 42 + 0x11 bytes     C#

IdeaBlade.EntityModel.SL!IdeaBlade.EntityModel.EntityAspect.OnPropertyChanged(System.ComponentModel.PropertyChangedEventArgs args = {System.ComponentModel.PropertyChangedEventArgs}) + 0x45 bytes     

IdeaBlade.EntityModel.SL!IdeaBlade.EntityModel.EntityAspect.add_PropertyChanged.AnonymousMethod(object o = {DealPricing: 18485}, System.ComponentModel.PropertyChangedEventArgs args = {System.ComponentModel.PropertyChangedEventArgs}) + 0x26 bytes     

IdeaBlade.EntityModel.SL!IdeaBlade.EntityModel.EntityWrapper.OnEntityAspectPropertyChanged(string propertyName = "IsChanged") + 0x92 bytes     

IdeaBlade.EntityModel.SL!IdeaBlade.EntityModel.EntityWrapper.EntityState.set(IdeaBlade.EntityModel.EntityState value = Unchanged) + 0x77 bytes     

IdeaBlade.EntityModel.SL!IdeaBlade.EntityModel.EntityWrapper.ReplaceAll(IdeaBlade.EntityModel.EntityWrapper sourceEntity = {DealPricing: 18485}, bool copy = true) + 0x9f bytes     

IdeaBlade.EntityModel.SL!IdeaBlade.EntityModel.EntityWrapper.ReplaceEntity(IdeaBlade.EntityModel.EntityWrapper sourceEntity = {DealPricing: 18485}, IdeaBlade.EntityModel.MergeStrategy mergeStrategy = OverwriteChanges) + 0x71 bytes     

IdeaBlade.EntityModel.SL!IdeaBlade.EntityModel.EntityGroup.ImportEntity(IdeaBlade.EntityModel.EntityWrapper sourceWrapper = {DealPricing: 18485}, IdeaBlade.EntityModel.MergeStrategy mergeStrategy = OverwriteChanges) + 0x89 bytes     

IdeaBlade.EntityModel.SL!IdeaBlade.EntityModel.EntityManager.SaveEntitiesPostProcessing(IdeaBlade.EntityModel.SaveWorkState workstate = {IdeaBlade.EntityModel.SaveWorkState}) + 0x795 bytes     

IdeaBlade.EntityModel.SL!IdeaBlade.EntityModel.EntityManager.SaveChangesAsyncCore.AnonymousMethod(IdeaBlade.EntityModel.EntitySavedEventArgs args = {IdeaBlade.EntityModel.EntitySavedEventArgs}) + 0x51 bytes     

IdeaBlade.EntityModel.SL!IdeaBlade.EntityModel.AsyncProcessor<IdeaBlade.EntityModel.EntitySavedEventArgs>.Execute.AnonymousMethod(object x = {IdeaBlade.EntityModel.EntitySavedEventArgs}) + 0x73 bytes     

[Native to Managed Transition]     

[Managed to Native Transition]     

mscorlib.dll!System.Delegate.DynamicInvokeImpl(object[] args = {object[1]}) + 0xb4 bytes     

mscorlib.dll!System.Delegate.DynamicInvoke(object[] args = {object[1]}) + 0x2a bytes     

System.Windows.dll!System.Windows.Threading.DispatcherOperation.Invoke() + 0x47 bytes     

System.Windows.dll!System.Windows.Threading.Dispatcher.Dispatch(System.Windows.Threading.DispatcherPriority priority = 13) + 0x161 bytes     

System.Windows.dll!System.Windows.Threading.Dispatcher.OnInvoke(object context = null) + 0x28 bytes     

System.Windows.dll!System.Windows.Hosting.CallbackCookie.Invoke(object[] args = {object[0]}) + 0x37 bytes     

System.Windows.dll!System.Windows.Hosting.DelegateWrapper.InternalInvoke(object[] args = {object[0]}) + 0x2a bytes     

System.Windows.Browser.dll!System.Windows.Hosting.ScriptingInterface.InvokeDelegate(System.Windows.Hosting.DelegateWrapper delegateWrapper = {System.Windows.Hosting.CallbackCookie}, System.Windows.Hosting.NativeMethods.ScriptParam[] pParams = {System.Windows.Hosting.NativeMethods.ScriptParam[0]}, ref System.Windows.Hosting.NativeMethods.ScriptParam pResult = {System.Windows.Hosting.NativeMethods.ScriptParam}) + 0x68 bytes     

System.Windows.Browser.dll!System.Windows.Hosting.ManagedHost.InvokeDelegate(System.IntPtr pHandle = 151065016, int nParamCount = 0, System.Windows.Hosting.NativeMethods.ScriptParam[] pParams = {System.Windows.Hosting.NativeMethods.ScriptParam[0]}, ref System.Windows.Hosting.NativeMethods.ScriptParam pResult = {System.Windows.Hosting.NativeMethods.ScriptParam}) + 0x124 bytes     

[Appdomain Transition]     

[Native to Managed Transition]     

Thanks, Simon.