Binding a property in datatemplate via a named control caused memory leak

[lfeng1420]

Describe the bug

When binding a property from viewmodel in datatemplate through a named control, memory leak occured. see below code:

<ListBox x:Name="elems" ItemsSource="{Binding Elements}">
        <ListBox.ItemTemplate>
            <DataTemplate DataType="vm:Element">
                <Grid ColumnDefinitions="Auto,*,Auto">
                    <CheckBox IsChecked="{Binding IsSelected}" />
                    <TextBlock
                        Grid.Column="1"
                        VerticalAlignment="Center"
                        Text="{Binding Text}" />
                    <TextBlock
                        Grid.Column="2"
                        VerticalAlignment="Center"
                        Text="{Binding #elems.((vm:MainViewModel)DataContext).Greeting}" />
                </Grid>
            </DataTemplate>
        </ListBox.ItemTemplate>
    </ListBox>

if replace '#elems' with '$parent[ListBox]', everything will be fine.

To Reproduce

1. clone this repo
2. build project and run
3. scroll from home to end, then from end to home (see below video)

repeat step 3 multiple times, and you will see Process Memory stays high and never fall back

memory-leak.mov

Expected behavior

no memory leak occurs.

Avalonia version

11.0.10

OS

Windows

Additional context

No response

[timunie]

test also 11.1 beta pls

[workgroupengineering]

Same as #15443

[lfeng1420]

test also 11.1 beta pls

i tried 11.1.0-beta1, also exists.

[lfeng1420]

Same as #15443

oh, i'll close this issue

[BAndysc]

I am not sure it is the same leak, I think it is a different thing. I think it is better to keep it open, memory leaks are a big problem, better keep track of all repros.

[BAndysc]

This leak is caused by NamedElementNode keeping a strong reference via _value

Avalonia/src/Avalonia.Base/Data/Core/ExpressionNodes/ExpressionNode.cs

Line 15 in a32a872

private object? _value = AvaloniaProperty.UnsetValue;

so it is a different problem than #15443

Looks like it was introduced with binding refactor

[lfeng1420]

I am not sure it is the same leak, I think it is a different thing. I think it is better to keep it open, memory leaks are a big problem, better keep track of all repros.

reopen now~

[maxkatz6]

@BAndysc note, you attached file from 11.1 version, while this issue is reproduced on 11.0.

11.0.10 code doesn't seem to use strong references there: https://github.com/AvaloniaUI/Avalonia/blob/11.0.10/src/Avalonia.Base/Data/Core/ExpressionNode.cs

[BAndysc]

That's true, I didn't take a look at 11.0 branch, and also, my conclusion that the leak is caused by NamedElementNode having a strong reference is not accurate, to say the least. I mean, it is the whole path from root which matters. A screenshot if it is any help:

The right path shows a leak where named binding is involved, with my zero knowledge about styling and binding system, I can't tell where the leak "begins".

As a non paying user I am not in position to complain, but imho those leaks are quite a big problem, affecting vast majority of the user base (even if they are unaware).

[timunie]

We're nit saying these leaks couldn't get a problem. So better to fix them st some point in time. If you want to help us speeding it up, you can also add your sample into src/Samples/Sandbox and try to debug it. From there you can step through the whole binding path. Again, I don't force anyone to do that, just an idea.