Fix datagrid not updating when not attached to tree

[almightyju]

What does the pull request do?

Makes datagrid datasource changes work when not attached to the visual tree

What is the current behavior?

When a datagrid is detached from the visual tree changes to the datasouce are not reflected when re attached

What is the updated/expected behavior with this PR?

Changed made to the datasource should be visible

How was the solution implemented (if it's not obvious)?

Checklist

• Added unit tests (if possible)?
• Added XML documentation to any related classes?
• Consider submitting a PR to https://github.com/AvaloniaUI/Documentation with user documentation

Breaking changes

Obsoletions / Deprecations

Fixed issues

Fixes #9527

[avaloniaui-team]

You can test this PR using the following package version. 11.0.999-cibuild0037344-beta. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]

[liugangnhm]

it seems that the issue has been fixed

[liugangnhm]

if i move the datagrid to another UserControl， this issue is still there

AvaloniaDataGridTest.zip

@maxkatz6

[timunie]

@liugangnhm your sample is still using 11.0.0. The fix will only be available in next release. You can try nightly builds for now.

[liugangnhm]

@liugangnhm your sample is still using 11.0.0. The fix will only be available in next release. You can try nightly builds for now.

ok，i will try later

[liugangnhm]

@liugangnhm your sample is still using 11.0.0. The fix will only be available in next release. You can try nightly builds for now.

yes, i works with nightly builds, thanks , i thought is had beed fixed in 11.0.0

[IZIDIA]

Hello. These changes led to the following bugs:
#16139 and #15218

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[almightyju]

@IZIDIA this change was never going to be great at performance with large data sets, I'm not sure why the scrolling doesn't work correctly.

From memory I think the only option was to not unwire events on detaching from the tree but that broke some tests to do with the grid not being released from memory

You could always try and make a buffer of events that ran while not attached to the tree and then process that buffer on attach. Should theoretically work and not need to reinitialise everything

[IZIDIA]

@almightyju I made the following changes and it actually works. When data changes (if we are detached from the tree), it is updated and the scroll position is saved. The whole solution is to update only the lines. #16140