DynamicResource not working for custom type property in Xamarin

Question

We have tried to bind dynamic resource for my custom class properties. But DynamicResource working fine for object type property, but not working for double type property. See my code below.

You can confirm the dynamic resource not set for PropertyA, by setting break point for PropertyA property change method.

For PropertyB property change method, break point hit with dynamic resource value.

 <ContentPage.Resources>
        <ResourceDictionary>
            <x:Double x:Key="MediumFont">25</x:Double>
        </ResourceDictionary>
    </ContentPage.Resources>

    <StackLayout>
                
        <local:TestClass >
            <local:TestClass.HintStyle>
                <local:LabelStyle PropertyA="{DynamicResource MediumFont}" PropertyB="{DynamicResource MediumFont}"/>
            </local:TestClass.HintStyle>
        </local:TestClass>
        
    
    </StackLayout>

 public class TestClass :View
    {

        public LabelStyle HintStyle
        {
            get => (LabelStyle)GetValue(HintStyleProperty);
            set => SetValue(HintStyleProperty, value);
        }

        public static readonly BindableProperty HintStyleProperty =
            BindableProperty.Create(nameof(HintStyle), typeof(LabelStyle), typeof(TestClass),
            new LabelStyle(), BindingMode.Default);
    }

    public class LabelStyle :View
    {
        public double PropertyA
        {
            get => (double)GetValue(PropertyAProperty);
            set => SetValue(PropertyAProperty, value);
        }

        public static readonly BindableProperty PropertyAProperty =
           BindableProperty.Create(nameof(PropertyA), typeof(double), typeof(LabelStyle), 
               0d, BindingMode.Default, null, OnPropertyAChanged);
        private static void OnPropertyAChanged(BindableObject bindable, object oldValue, object newValue)
        {
        }

        public object PropertyB
        {
            get => GetValue(PropertyBProperty);
            set => SetValue(PropertyBProperty, value);
        }

        private static readonly BindableProperty PropertyBProperty =
            BindableProperty.Create(nameof(PropertyB), typeof(object), typeof(LabelStyle),
            null, BindingMode.Default, null, OnPropertyBChanged);

        private static void OnPropertyBChanged(BindableObject bindable, object oldValue, object newValue)
        {
        }
    }

Please help me. Why the dynamic resource not working for PropertyA.

Answer 1

Solution1:

Use StaticResource instead of DynamicResource. The dynamic resource stores the Key, in this case "MediumFont", which is a string, and hence won't bind to a property of type double.

  <local:TestClass>
            <local:TestClass.HintStyle>
                <local:LabelStyle PropertyA="{StaticResource MediumFont}" PropertyB="{StaticResource MediumFont}"/>
            </local:TestClass.HintStyle>
        </local:TestClass>

Solution2:

When use DynamicResource, we have to use type object for the bindable property type. And then set the PropertyAProperty to private.

  public object PropertyA
    {
        get => GetValue(PropertyAProperty);
        set => SetValue(PropertyAProperty, value);
    }

    private static readonly BindableProperty PropertyAProperty =
       BindableProperty.Create(nameof(PropertyA), typeof(object), typeof(LabelStyle),
          null, BindingMode.Default, null, OnPropertyAChanged);
    private static void OnPropertyAChanged(BindableObject bindable, object oldValue, object newValue)
    {
    }