OnPropertyChanged is called twice if we use the ViewModelToModel attribute about catel.fody

[GeertvanHorrik]

Could it be because it's actually called "Property"? There is an "OnPropertyChanged" virtual method and the property is called OnPropertyChanged. Or does it happen to any sort of property name?

[Green7]

the name of the property does not matter.

[GeertvanHorrik]

I've written reproducable unit tests. Will investigate why this happens.

[GeertvanHorrik]

Generated code:

public object MyProperty
{
	[CompilerGenerated]
	get
	{
		return <MyProperty>k__BackingField;
	}
	[CompilerGenerated]
	set
	{
		<MyProperty>k__BackingField = value;
		OnMyPropertyChanged();
		RaisePropertyChanged("MyProperty");
	}
}

[GeertvanHorrik]

It also seems to happen to Catel 5 (according to the unit tests). It's probably because the ObservableObject does not do a equality check before raising the property.

There could be 2 solutions here (but I think both need to be fixed in Catel itself):

1. Get value before assigning in the model (but it will be "more expensive")
2. Add equality checks in ObservableObject setters (bonus)

[Green7]

Yes, ObservableObject does not check the old value before setting it again.
But I don't understand why the line: Model.Property = "test"; causes the value to be set twice?

[GeertvanHorrik]

It only happens to ObservableObject (not ModelBase) because the ModelBase does equality checks under the hood. I think the best way to solve this is in the ViewModelBase since we can never rely on any model handling this correctly.

[GeertvanHorrik]

Closing this ticket in favor of the Catel one (this will be (is actually) fixed in Catel itself).

[GeertvanHorrik]

btw the other request is covered by #357 , but that will only solve this issue when using the Catel one. If you use any others, it would still fail (hence the fix in Catel itself).

[Green7]

Ok, I'm waiting for a fix in Catel.