Use IValueConverter with DynamicResource?

Question

Is there a way to define a converter when using the DynamicResource extension? Something in the lines of

<RowDefinition Height="{Binding Source={DynamicResource someHeight}, Converter={StaticResource gridLengthConverter}}" />

which unfortunately gives me the following excpetion:

A 'DynamicResourceExtension' cannot be set on the 'Source' property of type 'Binding'. A 'DynamicResourceExtension' can only be set on a DependencyProperty of a DependencyObject.

Answer 1

I know i am really late to this but what definitely works is using a BindingProxy for the DynamicResource like this

<my:BindingProxy x:Key="someHeightProxy" Data="{DynamicResource someHeight}" />

Then applying the converter to the proxy

<RowDefinition Height="{Binding Source={StaticResource someHeightProxy}, Path=Data, Converter={StaticResource gridLengthConverter}}" />

Answer 2

Try something like that:

Markup extension:

public class DynamicResourceWithConverterExtension : DynamicResourceExtension
{
    public DynamicResourceWithConverterExtension()
    {
    }

    public DynamicResourceWithConverterExtension(object resourceKey)
            : base(resourceKey)
    {
    }

    public IValueConverter Converter { get; set; }
    public object ConverterParameter { get; set; }

    public override object ProvideValue(IServiceProvider provider)
    {
        object value = base.ProvideValue(provider);
        if (value != this && Converter != null)
        {
            Type targetType = null;
            var target = (IProvideValueTarget)provider.GetService(typeof(IProvideValueTarget));
            if (target != null)
            {
                DependencyProperty targetDp = target.TargetProperty as DependencyProperty;
                if (targetDp != null)
                {
                    targetType = targetDp.PropertyType;
                }
            }
            if (targetType != null)
                return Converter.Convert(value, targetType, ConverterParameter, CultureInfo.CurrentCulture);
        }

        return value;
    }
}

XAML:

<RowDefinition Height="{my:DynamicResourceWithConverter someHeight, Converter={StaticResource gridLengthConverter}}" />