NullToVisibility

EmptyObjectToObjectConverter.cpp

// From https://github.com/Dylan-H/NotePadUWP/
#include "pch.h"
#include "EmptyObjectToObjectConverter.h"
#include "ConverterTools.h"
namespace winrt::NotePad::implementation
{
	DependencyProperty EmptyObjectToObjectConverter::_NotEmptyValueProperty =
		DependencyProperty::Register(L"NotEmptyValue", winrt::xaml_typename<IInspectable>(), winrt::xaml_typename<NotePad::EmptyObjectToObjectConverter>(),  PropertyMetadata(nullptr));
	DependencyProperty EmptyObjectToObjectConverter::_EmptyValueProperty =
		DependencyProperty::Register(L"EmptyValue", winrt::xaml_typename<IInspectable>(), winrt::xaml_typename<NotePad::EmptyObjectToObjectConverter>(),  PropertyMetadata(nullptr));

    IInspectable EmptyObjectToObjectConverter::Convert(IInspectable const& value, Interop::TypeName const& targetType, IInspectable const& parameter, hstring const& language)
    {
		auto isEmpty = CheckValueIsEmpty(value);

		// Negate if needed
		if (winrt::NotePad::ConverterTools::TryParseBool(parameter))
		{
			isEmpty = !isEmpty;
		}

		return winrt::NotePad::ConverterTools::Convert(isEmpty ? EmptyValue() : NotEmptyValue(), targetType);
    }

    IInspectable EmptyObjectToObjectConverter::ConvertBack(IInspectable const& value, Interop::TypeName const& targetType, IInspectable const& parameter, hstring const& language)
    {
        throw hresult_not_implemented();
    }

}

EmptyObjectToObjectConverter.h

// From https://github.com/Dylan-H/NotePadUWP/
#pragma once

#include "EmptyObjectToObjectConverter.g.h"


namespace winrt::NotePad::implementation
{
	using namespace winrt::Windows::UI::Xaml;
	using namespace winrt::Windows::Foundation;
    struct EmptyObjectToObjectConverter : EmptyObjectToObjectConverterT<EmptyObjectToObjectConverter>
    {
        EmptyObjectToObjectConverter() = default;

		IInspectable NotEmptyValue() { { return GetValue(_NotEmptyValueProperty); } };
		void NotEmptyValue(IInspectable const& value) { SetValue(_NotEmptyValueProperty, value); };
        IInspectable EmptyValue() { return GetValue(_EmptyValueProperty); };
        void EmptyValue(IInspectable const& value) { SetValue(_EmptyValueProperty, value); };
        IInspectable Convert(IInspectable const& value, Interop::TypeName const& targetType, IInspectable const& parameter, hstring const& language);
        IInspectable ConvertBack(IInspectable const& value, Interop::TypeName const& targetType, IInspectable const& parameter, hstring const& language);
		virtual bool CheckValueIsEmpty(IInspectable value)
		{
			return value == nullptr;
		}
		static DependencyProperty NotEmptyValueProperty() { return _NotEmptyValueProperty; };
        static DependencyProperty EmptyValueProperty() { return _EmptyValueProperty; };
	private:
		static DependencyProperty _NotEmptyValueProperty;
		static DependencyProperty _EmptyValueProperty;
    };
}

namespace winrt::NotePad::factory_implementation
{
    struct EmptyObjectToObjectConverter : EmptyObjectToObjectConverterT<EmptyObjectToObjectConverter, implementation::EmptyObjectToObjectConverter>
    {
    };
}

EmptyObjectToObjectConverter.idl

// From https://github.com/Dylan-H/NotePadUWP/
namespace NotePad
{
	[default_interface] 
	runtimeclass EmptyObjectToObjectConverter : Windows.UI.Xaml.DependencyObject, Windows.UI.Xaml.Data.IValueConverter
	{
		EmptyObjectToObjectConverter();
		static Windows.UI.Xaml.DependencyProperty NotEmptyValueProperty{ get; };
		static Windows.UI.Xaml.DependencyProperty EmptyValueProperty{ get; };
		Object NotEmptyValue;
		Object EmptyValue;
	}
}