Editable combo box sets bound value to null when itemsource changes

[SoggyBottomBoy]

Describe the bug

I have an editable combo box which allows the user to select predefined items or set another item by typing in its name. The combox box ItemsSource is bound to a list of strings which is changed when action is taken by the user which changes the list of predefined strings. When the ItemsSources changes it appears that the SelectedItem is set to null. I am unable to re-type the same value, and clicking the drop down repopulates the value.

I'm pretty confused about what is going on...

Steps to reproduce the bug

Create 2 editable combo boxes.
Have one 1 combo box ItemsSource rely on the value of the other.
Enter a value like "1" in the combo box.
Change the value of the other combo box to trigger a changes of the items source
The value in the editable combo box is replaced with null and "1" can not be entered.

Expected behavior

For an editable combo box change the items source should not re-trigger the value bound to selected item or text to change.

Screenshots

No response

NuGet package version

WinUI 3 - Windows App SDK 1.5.2: 1.5.240404000

Windows version

Windows 11 (22H2): Build 22621

Additional context

No response

[github-actions]

Hi I'm an AI powered bot that finds similar issues based off the issue title.

Please view the issues below to see if they solve your problem, and if the issue describes your problem please consider closing this one. Thank you!

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• Combobox binding issue in ContentControl (#8078), similarity score: 0.79

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[kmahone]

I am having a hard time understanding the repro steps. Could you share some code and xaml that demonstrates the issue?

[SoggyBottomBoy]

https://github.com/SoggyBottomBoy/EditableComboBoxBug
The second combox (bottom) is editable so enter in a value in the box, then change the section of the first box (top)

[kmahone]

Thanks. I can reproduce the issue.

As you said, there are two issues here:

1. When the ItemsSource changes, it resets the selection of the ComboBox. This usually makes sense, but in the case of an editable combobox, it probably should not happen.
2. The inner TextBox of the ComboBox retains its old value. Normally when a user enters a value into the TextBox, the ComboBox will use that for the selection. But, it relies on the TextBox's TextChanging to trigger that. In this case, if the text does not actually change, it won't trigger that logic. So in order to select the old value, the user has to intentionally change it to something else and then change it back.

[SoggyBottomBoy]

Yep but I think item 2 is somewhat solved by item 1. I would say an editable combox should be expected to retain the value if the ItemsSource is changed, if the developer does not want this behaviour then it should be an explicit opt in by handling ItemsSourceChanged or similar.