IUnknown is an ambiguous symbol

[nlogozzo]

Hi all,
I'm trying to get my C++ WinUI 3 Win32 app to work with a FolderPicker. I included #include <shobjidl.h> to set up my FolderPicker:

IAsyncAction MainWindow::MenuOpenFolder(const IInspectable& sender, const RoutedEventArgs& e)
    {
        FolderPicker folderPicker;
        folderPicker.as<IInitializeWithWindow>()->Initialize(GetActiveWindow());
        folderPicker.FileTypeFilter().Append(L"*");
        StorageFolder result = co_await folderPicker.PickSingleFolderAsync();
        if (result)
        {
            Configuration config = Configuration::LoadConfiguration();
            std::string folderPath = to_string(result.Path());
            m_musicFolder.FolderPath(folderPath);
            config.PreviousMusicFolderPath(folderPath);
            LblStatus().Text(result.Path());
            Configuration::SaveConfiguration(config);
            MenuRefreshFolder(nullptr, nullptr);
        }
    }

However, I'm getting a IUnknown is an ambiguous symbol error as a result of including that file.
This is my pch.h file for reference as well:

#pragma once

#include <windows.h>
#include <unknwn.h>
#include <restrictederrorinfo.h>
#include <hstring.h>

// Undefine GetCurrentTime macro to prevent
// conflict with Storyboard::GetCurrentTime
#undef GetCurrentTime

#include <winrt/Microsoft.UI.Composition.h>
#include <winrt/Microsoft.UI.Xaml.h>
#include <winrt/Microsoft.UI.Xaml.Controls.h>
#include <winrt/Microsoft.UI.Xaml.Controls.Primitives.h>
#include <winrt/Microsoft.UI.Xaml.Data.h>
#include <winrt/Microsoft.UI.Xaml.Interop.h>
#include <winrt/Microsoft.UI.Xaml.Markup.h>
#include <winrt/Microsoft.UI.Xaml.Media.h>
#include <winrt/Microsoft.UI.Xaml.Navigation.h>
#include <winrt/Microsoft.UI.Xaml.Shapes.h>
#include <winrt/Windows.ApplicationModel.Activation.h>
#include <winrt/Windows.Foundation.h>
#include <winrt/Windows.Foundation.Collections.h>
#include <winrt/Windows.Storage.Pickers.h>
#include <winrt/Windows.System.h>
#include <winrt/Windows.UI.Xaml.Interop.h>

How can I fix the ambiguity?

[RealTommyKlein]

You'd need to disambiguate based on what kind of IUnknown you're expecting (::IUnknown for the ABI version, or ::winrt::Windows::Foundation::IUnknown for the C++/WinRT struct). The shobjidl.h header expects the ABI version, so you may be able to resolve this with something like using IUnknown = ::IUnknown;. @Scottj1s may also have a better idea of how to resolve this.

[nlogozzo]

@RealTommyKlein I changed the method to something like this:

IAsyncAction MainWindow::MenuOpenFolder(const IInspectable& sender, const RoutedEventArgs& e)
    {
        FolderPicker folderPicker;
        {
            using IUnknown = ::IUnknown;
            folderPicker.as<IInitializeWithWindow>()->Initialize(GetActiveWindow());
        }
        folderPicker.FileTypeFilter().Append(L"*");
        StorageFolder result = co_await folderPicker.PickSingleFolderAsync();
        if (result)
        {
            Configuration config = Configuration::LoadConfiguration();
            std::string folderPath = to_string(result.Path());
            m_musicFolder.FolderPath(folderPath);
            config.PreviousMusicFolderPath(folderPath);
            LblStatus().Text(result.Path());
            Configuration::SaveConfiguration(config);
            MenuRefreshFolder(nullptr, nullptr);
        }
    }

And i'm still getting the issue. I also moved it to the top of the window same thing

[RealTommyKlein]

It'd need to be in your precompiled header instead of the place you're using it, since I'm guessing the error is happening when including the shobjidl.h header. But the real issue is probably something in your code like:

using namespace winrt::Windows::Foundation;

That allows the WinRT IUnknown to be referenced without fully qualifying its namespace, causing ambiguity with the ABI IUnknown.

[nlogozzo]

Removing using namespace winrt::Windows::Foundation; from MainWindow.xaml.cpp solved my issue