AdvancedCollection inserts elements at wrong position when the element is added at the end of the source collection

[abdes]

Describe the bug

In AdvancedCollection.cs,

        private bool HandleItemAdded(int newStartingIndex, object newItem, int? viewIndex = null)
        {
...
                else if (newStartingIndex == _source.Count - 1)
                {
                    newViewIndex = _view.Count - 1;
                }
...
}

When an item is added at the end of the source collection (i.e. _source.Count -1), the AdvancedCollection will insert it at the position _view.Count - 1, which is the position just before the last item in the view. This is not correct and results in the items order not respecting the source collection order, if the view does not use sorting.

Regression

No response

Reproducible in sample app?

• [ ] This bug can be reproduced in the sample app.

Steps to reproduce

Please refer to the source code above, it's obvious.

Expected behavior

The expected behavior is that the item is added at the end of the collection.

Screenshots

No response

Windows Build Number

• [ ] Windows 10 1809 (Build 17763)
• [ ] Windows 10 1903 (Build 18362)
• [ ] Windows 10 1909 (Build 18363)
• [ ] Windows 10 2004 (Build 19041)
• [ ] Windows 10 20H2 (Build 19042)
• [ ] Windows 10 21H1 (Build 19043)
• [ ] Windows 11 21H2 (Build 22000)
• [ ] Other (specify)

Other Windows Build number

No response

App minimum and target SDK version

• [ ] Windows 10, version 1809 (Build 17763)
• [ ] Windows 10, version 1903 (Build 18362)
• [ ] Windows 10, version 1909 (Build 18363)
• [ ] Windows 10, version 2004 (Build 19041)
• [ ] Other (specify)

Other SDK version

No response

Visual Studio Version

No response

Visual Studio Build Number

No response

Device form factor

No response

Nuget packages

CommunityToolkit.WinUI.Collections 8.0.240109

Additional context

No response

Help us help you

No.

[ghost]

Hello abdes, thank you for opening an issue with us!

I have automatically added a "needs triage" label to help get things started. Our team will analyze and investigate the issue, and escalate it to the relevant team if possible. Other community members may also look into the issue and provide feedback 🙌

[abdes]

Also see: https://github.com/CommunityToolkit/Windows/issues/317

[Arlodotexe]

Closed as duplicate of https://github.com/CommunityToolkit/Windows/issues/317