MVVM Toolkit warning MVVMTK0045

Fields using [ObservableProperty] will generate code that is not AOT compatible in WinRT scenarios (such as UWP XAML and WinUI 3 apps), and partial properties should be used instead (as they allow the CsWinRT generators to correctly produce the necessary WinRT marshalling code).

The following sample generates MVVMTK0045:

using CommunityToolkit.Mvvm.ComponentModel;

namespace MyApp;

public partial class SampleViewModel : ObservableObject
{
    [ObservableProperty]
    private string? name;
}

You should instead make that field a partial property (eg. named Name), like so:

using CommunityToolkit.Mvvm.ComponentModel;

namespace MyApp;

public partial class SampleViewModel : ObservableObject
{
    [ObservableProperty]
    public partial string? Name { get; set; }
}

Additional resources

• You can find more examples in the unit tests.