Generated code tries to assign to a read only `ObservableCollection`

[karmeye]

Describe the bug

This code

[ObservableObject]
public partial class MyViewModel : ViewModel
{
  public ObservableCollection<DataType> SelectedItems { get;  } = [];
}

results in error:

CS0200 Property or indexer "cannot be assigned to" "it is read only"

in the owner of the MyViewModel:

private void UpdateTwoWay_5_ItemsSource()
{
    if (this.initialized)
    {
        if (this.dataRoot != null)
        {
            if (this.dataRoot.ViewModel != null)
            {
                if (this.dataRoot.ViewModel.MyViewModel!= null)
                {
                    // Error here
                    this.dataRoot.ViewModel.MyViewModel.SelectedItems = (global::System.Collections.ObjectModel.ObservableCollection<global::Abc>)this.obj5.ItemsSource;
                }
            }
        }
    }
}

Regression

No response

Steps to reproduce

1. Do the above.

I'm using NuGet package: CommunityToolkit.Mvvm 8.2.2

Expected behavior

As I understand it, with collections you don't use, e.g., a List marked with ObservableProperty, you just do it the standard way with an ObservableCollection, and therefore it is only assigned once. So it should work to not have a setter.

Screenshots

No response

IDE and version

VS 2022

IDE version

Microsoft Visual Studio Community 2022 (64-bit) - Current Version 17.9.2

Nuget packages

• [ ] CommunityToolkit.Common
• [ ] CommunityToolkit.Diagnostics
• [ ] CommunityToolkit.HighPerformance
• [X] CommunityToolkit.Mvvm (aka MVVM Toolkit)

Nuget package version(s)

8.2.2

Additional context

Adding a setter seems to make everything work.

Help us help you

No, just wanted to report this

[Sergio0694]

That code is generated by the XAML compiler, not by the MVVM Toolkit. The issue is it doesn't support init only properties.