What is wrong with this code

Question

I ported an app from C++/CX to C++/WinRT, And the basic code is this (Excluding Main()):

class DirectXApp : public IFrameworkView
{. . .};
class DirectXAppSource : IFrameworkViewSource
{
virtual IFrameworkView : CreateView()
{
return new DirectXApp();
}
}

And these 2 errors show up:
Severity Code Description Project File Line Suppression State
Error C2664 'void winrt::Windows::ApplicationModel::Core::CoreApplication::Run(const winrt::Windows::ApplicationModel::Core::IFrameworkViewSource &)': cannot convert argument 1 from 'DirectXAppSource *' to 'const winrt::Windows::ApplicationModel::Core::IFrameworkViewSource &' CoreApp