communitytoolkitrepro1

This repository attempts to reproduce the problems in the CommunityToolkit.MAUI project outlined in the following discussion: CommunityToolkit/Maui#546

Issue

The issue appears to be that when an object that was created as a subclass of another object is passed through the navigation dictionary, (a) [QueryProperty] causes an outright crash of the application, and (b) using IQueryAttributable to manually copy the parameter does not invoke OnPropertyChanged automatically.

Current State

The committed code is in the "not working" state. Launch the application and see two names in the MainPage list. Tap any name to move to a detail page, passing the Character object to the DetailPage. Note that no name is displayed in the DetailPage UI.

Tests

1. Comment IN the OnPropertyChanged line in DetailViewModel.cs to see the name start loading in the DetailPage UI. [This is annotated as REPRO (3)].

2. Remove the IQueryAttributable interface, then comment in the [QueryProperty] on the DetailViewModel. Run the application, tap on a name, and note that the entire application will crash. [This is annoted as REPRO (1)].

3. Go to MainViewModel.cs and change the instances of SubCharacter back to the parent class Character when being new'd up in the constructor. Make sure your [QueryProperty] is still commented IN on the DetailViewModel. Run the application and everything will work as expected, and the name will display on the DetailPage.