How can I use an ObservableObject as a Binding Target in code and XAML in WinUI 3?-CodePudding

How can I use an ObservableObject (from Community Toolkit) as a Binding Target in code and XAML in a WinUI 3 Desktop app?

Here's a simple (partial) homepage example:

<!-- Home.xaml -->
<Page
    x:Class="PFSI.Views.Home"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:vms="using:PFSI.ViewModels"
    mc:Ignorable="d" >
    
    <Page.DataContext>
        <vms:HomeViewModel x:Name="ViewModel" />
    </Page.DataContext>
    
    <Grid x:Name="ContentArea" >
        <TextBlock x:Name="TBox" Text="This text should be shaded." Foreground="{Binding Shade}" />
    </Grid>
</Page>

// Home.xaml.cs
public partial class HomePage : Page
{
    public HomePage()
    {
        InitializeComponent();
    }
}

// HomeViewModel.cs
public class HomeViewModel : ObservableObject
{
    public HomeViewModel()
    {
        Classes.TraceListener.TraceMessage(GetType().Name);
    }

    [ObservableProperty]
    private SolidColorBrush shade;
}

Using the property Shade as a source is straightforward in XAML (see the TextBlock in Home.xaml) or in code:

Binding bBinding = new() { Path = new PropertyPath("Shade"), Source = ViewModel, Mode = BindingMode.OneWay };
TBox.SetBinding(TextBox.ForegroundProperty, bBinding);

But what if I want to make the property Shade the target of the binding (that is, I want to set Shade with the binding)?

BindingOperations.SetBinding(DependencyObject target, DependencyProperty dp, BindingBase binding) requires a DependencyObject (which HomeViewModel is not, it's an ObservableObject) and a DependencyProperty identifier (which Shade doesn't have as it's a normal property).

I'm sure this is possible but I'm at a loss for the moment. Any help most welcome.

CodePudding user response：

How can I use an ObservableObject (from Community Toolkit) as a Binding Target in code and XAML in a WinUI 3 Desktop app?

You can't since the target property of a binding must be a dependency property.

I'm sure this is possible ...

Not without turning the target property into a dependency property (and the class into a DependencyObject).

I don't see why you would need to extend both ObservableObject and DependencyObject though. It's one or the other, i.e. either your class is some kind of view model or some kind of control.