microsoft/microsoft-ui-xaml

x:Bind and DataTemplates updating two way bindings incorrectly for selector based controls

Opened this issue · 1 comments

tkillingerAlro commented

Describe the bug

When using x:Bind with DataTemplates collection based controls are resetting selected items to null. This has been happening since I started using the Windows App SDK around version 1.0 and is becoming increasingly hard to code around.

Ones I have noticed are Combobox and ListView (I'm sure there are others). This seems to be related to the Selector Base Class.

https://learn.microsoft.com/en-us/windows/windows-app-sdk/api/winrt/microsoft.ui.xaml.controls.primitives.selector?view=windows-app-sdk-1.6

I have tried to look into the generated code and it seems like the following is happening.

  1. A DataTemplates base binding object is set to another object due to the reuse of cached DataTemplates.
  2. Selector based sub template controls check if the selected item is in the base binding object's new collection.
  3. It's not due to the change of the whole binding object changing.
  4. Selected Item is set to null

I have attached a sample project to demonstrate this.
This issue exists in standard WinUI controls and the Windows Community Toolkit ListDetailsView

Steps to reproduce the bug

  1. Open up example project
  2. Go to "x:Bind Control INotifyPropertyChanged" page
  3. Click on the different list items change
  4. You should notice the sub lists "Selected ***: value" TextBlocks are changing to Null
  5. Go to "x:Bind Data Template" page
  6. Click on the different list items change.
  7. You should notice the sub lists "Selected ***: value" TextBlocks are changing to Null

Expected behavior

When using x:Bind in a DataTemplate the selected items should not be set to null. DataTemplates may contain a multitude of selector based sub controls. Leads to a mess in the ViewModel when trying to determine if the user changed something on the screen.

Screenshots

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ItemSourceBindingIssues.zip

NuGet package version

None

Packaging type

No response

Windows version

No response

IDE

Visual Studio 2022

Additional context

No response

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