Automatically detaching behaviors

[EmmanuelJego]

Hello!

This issue is more of a question than a bug report.

We are currently using several Behaviors within our X.Forms project, to do different things on VisualElements. We recently noticed that behaviors are not detached from their associated control automatically when the control is destroyed. Which seems normal according to the documentation (https://docs.microsoft.com/en-us/xamarin/xamarin-forms/app-fundamentals/behaviors/creating#removing-a-behavior-from-a-control).

behaviors are not implicitly removed from controls unless the control's Behaviors collection is modified by a Remove or Clear method

If we do not do that, the behavior is never destroyed, and the OnDetachingFrom method is not called. Which can leads to memory leaks.

To avoid that, we have to clear explicitly (manually) the Behaviors collection for each of our controls that have behaviors, for instance when the parent's page OnDisappearing method is called. But it seems very laborious, and in some cases it does not work: if the control that has behavior(s) is removed before the page disappears (a list item deletion for instance).

Now, to do that automatically, we built a class that inherits from Xamarin.Forms.Behavior<T> in which we override the OnAttachedTo method, to add a LifecycleEffect (from the Xamarin.CommunityToolkit) to the attached control. When the Unloaded event is raised, we can now clear the Behaviors collection of the control. All of our behaviors have to inherit from that class obviously.

It works, but we were wondering if this is right way to do it. We do not clearly understand why the behaviors are not automatically detached from the associated control when it is destroyed.

Is there something that we are missing? Or a better way to do it?

Thanks in advance for your help!

Emmanuel

[GalaxiaGuy]

I too would like to know the answer to this. At first glance it seems a pretty clean way to do it.

(I'm also curious why Behaviors are not automatically removed).

[jfversluis]

I think there is also more info and discussion about that for .NET MAUI: dotnet/maui#3968