using mediacapture in c++

Question

void MainPage::CameraInit()
{
	preview->Source = nullptr;
	try
	{
		auto mediacapture = ref new Windows::Media::Capture::MediaCapture();
		m_mediacapturemgr = mediacapture;
		create_task(m_mediacapturemgr->InitializeAsync()).then([this](task<void> initTask)
		{
			try
			{
				initTask.get();
				auto mediacapture = m_mediacapturemgr.Get();
			}
			catch (Exception^ e)
			{ 
			}
		});
	}
	catch (Exception^ e)
	{
		preview->Source = nullptr;
	}
}

void MainPage::CameraPreview()
{
	try
	{
		auto mediacapture = m_mediacapturemgr.Get();
		preview->Source = mediacapture;
		create_task(mediacapture->StartPreviewAsync()).then([this](task<void> previewTask)
		{
			try
			{
				previewTask.get();
				auto mediaCapture = m_mediacapturemgr.Get();
			}
			catch (Exception^ e)
			{
				preview->Source = nullptr;
			}
		});
	}
	catch (Exception^ e)
	{
		preview->Source = nullptr;
	}
}

Here is my code following the example of the MediaCapture from MSDN.

I have reduced a lot of code which is unnecessary for me into this and I am getting an error of "HRESULT:0xC00D36B6 This object needs to be initialized before the requested operation can be carried out" which the pointer points at the preview->Source = mediacapture; at the CameraPreview and I have searched on internet and still have no idea what is wrong with it.

namespace App4
{
	/// <summary>
	/// An empty page that can be used on its own or navigated to within a Frame.
	/// </summary>
	public ref class MainPage sealed
	{
	public:
		MainPage();
	private:
		void CameraInit();
		void CameraPreview();
		Platform::Agile<Windows::Media::Capture::MediaCapture> m_mediacapturemgr;
	};
}

and here is my .h file

Thanks in advance