Behavior bindable property with DynamicResource not supported?

[mattleibow]

Discussed in https://github.com/dotnet/maui/discussions/13691

^{Originally posted by **Cybrosys** March 4, 2023} Hi, I raised this Q&A and also a bug in the MCT repo: https://github.com/CommunityToolkit/Maui/discussions/1054 It is a question related to doing a `DynamicResource ` binding against a bindable property on the `StatusBarBehaior`, if it is supported or a bug. If it is a bug I think it belongs here in the main MAUI repo. Here is a link to the bug in the MCT Repo: https://github.com/CommunityToolkit/Maui/issues/1056 So, is this a bug in the MAUI repo or a limitation? For me as a developer and consumer, since the XAML does not show any error I would expect and assume that I would be able to use a `DynamicResource` binding for the `StatusBarBehavior`'s `StatusBarColor` bindable property. I also expressed in one of my comments that if I wanted to start investigating this, where would I start? I do not know who would own the `DynamicResource` binding. When doing a normal `Bind` I would expect it to be owned by the UI element itself, targeting a defined `BindingContext`. However, `DynamicResource` bindings seem a bit more "magical" in that they work without a `BindingContext` being defined/assigned. There are several issues currently related to `DynamicResource` bindings not working in .NET 7 but in .NET 6. So I do not know if this problem is related to `Behavor`s specifically or a core issue with `DynamicResource`. **Update** I got information here https://github.com/CommunityToolkit/Maui/issues/1056 that it can't use `DynamicResource` because it does not inherit from [VisualElement](https://github.com/dotnet/maui/blob/main/src/Controls/src/Core/VisualElement.cs#L770) or implement [IResourcesProvider](https://github.com/dotnet/maui/blob/main/src/Controls/src/Core/IResourcesProvider.cs). I would argue that you should be able to use `DynamicResource` even when not inheriting from `VisualElement`. The reason being that you can put any type of value into a `ResourceDictionary`, so in essence it is just a normal binding where the source is the parent or app's `ResourceDictionary`.

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• Make DynamicResource bindings be supported as normal bindings (#13724), similarity score: 0.87
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[mattleibow]

@mikeparker104 do you have a repro?

[mattleibow]

This may be a workaround:

public static class IconTintColor
{
    public static readonly BindableProperty TintColorProperty =
        BindableProperty.CreateAttached("TintColor", typeof(Color), typeof(IconTintColor), default,
            propertyChanged: OnTintColorChanged);

    private static void OnTintColorChanged(BindableObject bindable, object oldValue, object newValue)
    {
        if (bindable is not View view)
            return;

        if (view.Behaviors.OfType<IconTintColorBehavior>().FirstOrDefault() is { } existing)
        {
            existing.TintColor = (Color)newValue;
        }
        else
        {
            var behavior = new IconTintColorBehavior
            {
                TintColor = (Color)newValue
            };
            view.Behaviors.Add(behavior);
        }

    }

    public static Thickness GetTintColor(BindableObject view)
    {
        return (Thickness)view.GetValue(TintColorProperty);
    }

    public static void SetTintColor (BindableObject view, bool value)
    {
        view.SetValue(TintColorProperty, value);
    }
}

Used like:

<Image
    Source="dotnet_bot.png"
    HeightRequest="185"
    Aspect="AspectFit"
    SemanticProperties.Description="dot net bot in a race car number eight"
    local:IconTintColor.TintColor="{DynamicResource TargetColor}">
    <!-- <Image.Behaviors>
        <toolkit:IconTintColorBehavior TintColor="{DynamicResource TargetColor}" />
    </Image.Behaviors> -->
</Image>

[mikeparker104]

@mikeparker104 do you have a repro?

@mattleibow adding repro: https://github.com/mikeparker104/repro_23578