I have created a minimalist WinUI(3) WinRT/C++ Desktop (Blank, Packaged) and added a single UserControl. The module that is added compiles and runs just fine. But I want to deal with DependencyProperties so I'm trying to build up to that in small increments. My .idl file shows the runtimeclass inherits from winrt::Microsoft.UI.Xaml.Controls.UserControl but the .h file lacks the same inheritance in the struct definition. I can't figure out why I can't add the inheritance to the CalcButtonT in the implementation. When I do I get the error message that says:

static_assert failed: 'Class must derive from implements<> or ClassT<> where the first template parameter is the derived class name, e.g. struct D : implements<D, ...>'

What the error message fails to show is which class it is referring to. The build messages lead me to believe it is my CalcButton class. Also, when I have tried to add DependencyProperties to my CalcButton, I get a message that one of the steps in a OneWay mode must implement INotifyPropertyChange. But if I add the Microsoft::UI::Xaml::Data::INotifyPropertyChange to the inheritance, I get a message that it is already a base inheritance class.

Here are my four files. The remaining code within this project has been left untouched from the creation of my blank project. I am not trying to use my CalcButton, just get it up and building.

CalcButton.idl:

namespace ThirdCppAppv3
{
    [default_interface]
    runtimeclass CalcButton : Microsoft.UI.Xaml.Controls.UserControl
    {
        CalcButton();
    }
}

CalcButton.xaml:

<?xml version="1.0" encoding="utf-8"?>
<UserControl
    x:Class="ThirdCppAppv3.CalcButton"
    xmlns=";
    xmlns:x=";
    xmlns:local="using:ThirdCppAppv3"
    xmlns:d=";
    xmlns:mc=";
    mc:Ignorable="d">

    <StackPanel Orientation="Horizontal" HorizontalAlignment="Center" VerticalAlignment="Center">
        <Button x:Name="myButton" Click="myButton_Click" Content="Custom Button"></Button>
    </StackPanel>
</UserControl>

CalcButton.xaml.h:

#pragma once

#include "CalcButton.g.h"

namespace winrt::ThirdCppAppv3::implementation
{
    struct CalcButton : CalcButtonT<CalcButton, Microsoft::UI::Xaml::Controls::UserControl>
    {
        CalcButton();

        void myButton_Click(IInspectable const&, winrt::Microsoft::UI::Xaml::RoutedEventArgs const&);

    };
}

namespace winrt::ThirdCppAppv3::factory_implementation
{
    struct CalcButton : CalcButtonT<CalcButton, implementation::CalcButton>
    {
    };
}

CalcButton.xaml.cpp:

#include "pch.h"
#include "CalcButton.xaml.h"
#include "CalcButton.g.cpp"

using namespace winrt;
using namespace Microsoft::UI::Xaml;

// To learn more about WinUI, the WinUI project structure,
// and more about our project templates, see: .

namespace winrt::ThirdCppAppv3::implementation
{
    CalcButton::CalcButton()
    {

    }

    void CalcButton::myButton_Click(IInspectable const&, winrt::Microsoft::UI::Xaml::RoutedEventArgs const&)
    {

    }

}

It's got to be something stupid I can't see. It's also frustrating that I can't find any recent samples of UserControls

Peter