How to enumerate folder contents in Oct 2018 - c++-winrt

Question

Trying to translate to cppwinrt the StorageFolder method GetFilesAsync I'm unable to get past compiler link errors. Here is a very simple routine to test the concept:
#include "winrt/Windows.Storage.h"
#include "winrt/Windows.Foundation.Collections.h"
IAsyncAction TestClass::LoadFiles()
{
StorageFolder appFolder = Windows::ApplicationModel::Package::Current().InstalledLocation();
StorageFolder assetsFolder = co_await appFolder.GetFolderAsync(hstring(L"Assets"));
auto files = co_await assetsFolder.GetFilesAsync(CommonFileQuery::DefaultQuery);
}
The problem seems to lie in the return type for GetFilesAsync. I've tried various types for that, e.g. IVectorView, but nothing seems to work. Does anyone know of a code example showing how this enumeration might be accomplished in C++/winrt?
[UPDATE] Returning to this project with SDK 10.0.17666 and VS 15.9.0 Preview 3 I find that the solution adopted earlier from these answers no longer works. This time I will be sure to include the full error to see if anyone has ideas. For simplicity I'll use just the simple code provided by IInspectable, altered only to make it a class member in my ResourceManager class:
#include "winrt/Windows.ApplicationModel.h"
#include "winrt/Windows.Storage.h"
#include "winrt/Windows.Storage.Streams.h"
#include "winrt/Windows.Foundation.Collections.h"
#include "winrt/Windows.Storage.Search.h"
#include "winrt/Windows.UI.Core.h"
#include "pch.h"
using namespace winrt;
using namespace Windows::Foundation;
using namespace Windows::Storage;
using namespace Windows::Storage::Search;
IAsyncAction ResourceManager::LoadActivities()
{
StorageFolder appFolder = Windows::ApplicationModel::Package::Current().InstalledLocation();
StorageFolder assetsFolder = co_await appFolder.GetFolderAsync(L"Activities");
auto files = co_await assetsFolder.GetFilesAsync(CommonFileQuery::DefaultQuery);
}
The call to GetFilesAsync now produces the following link error:
Severity Code Description Project File Line Suppression State
Error LNK2019 unresolved external symbol "public: struct winrt::Windows::Foundation::IAsyncOperation > __thiscall winrt::impl::consume_Windows_Storage_Search_IStorageFolderQueryOperations::GetFilesAsync(enum winrt::Windows::Storage::Search::CommonFileQuery const &)const " (?GetFilesAsync#?$consume_Windows_Storage_Search_IStorageFolderQueryOperations#UStorageFolder#Storage#Windows#winrt###impl#winrt##QBE?AU?$IAsyncOperation#U?$IVectorView#UStorageFile#Storage#Windows#winrt###Collections#Foundation#Windows#winrt###Foundation#Windows#3#ABW4CommonFileQuery#Search#Storage#63##Z) referenced in function "public: struct winrt::Windows::Foundation::IAsyncAction __thiscall AppEngine::ResourceManager::LoadActivities$_ResumeCoro$2(void)" (?LoadActivities$_ResumeCoro$2#ResourceManager#AppEngine##QAE?AUIAsyncAction#Foundation#Windows#winrt##XZ)
(followed by the path to the object file)
I have to admit I find that error message hard to decipher. Perhaps someone else here will have an idea? Must be something that changed in recent system updates.

Answer 1

For what it's worth, the following standalone code builds just fine. So you're probably either missing a #include or a link library, but it's impossible to tell when you don't share important information like what actual error(s) you're seeing.
#pragma comment(lib, "WindowsApp")
#include <winrt/Windows.ApplicationModel.h>
#include <winrt/Windows.Foundation.Collections.h>
#include <winrt/Windows.Storage.h>
#include <winrt/Windows.Storage.Search.h>
using namespace winrt;
using namespace Windows::Foundation;
using namespace Windows::Storage;
using namespace Windows::Storage::Search;
IAsyncAction LoadFiles()
{
StorageFolder appFolder = Windows::ApplicationModel::Package::Current().InstalledLocation();
StorageFolder assetsFolder = co_await appFolder.GetFolderAsync(L"Assets");
auto files = co_await assetsFolder.GetFilesAsync(CommonFileQuery::DefaultQuery);
}
int main()
{
LoadFiles().get();
}