Http POST using C++

MainPage.xaml

<Page x:Class="FacePostProject.MainPage"
               xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
               xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
               xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
               xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
               mc:Ignorable="d"
               Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">

    <Grid>
        <StackPanel VerticalAlignment="Center" 
                             HorizontalAlignment="Center">
            <Button Content="Upload"
                             x:Name="UploadButton"
                             Margin="0,0,10,0"
                             Click="Send_Click" />
            <Button Content="Cancel"
                             x:Name="CancelButton"
                             IsEnabled="False"
                             Click="Cancel_Click" />
        </StackPanel>
    </Grid>
</Page>

MainPage.xaml.cpp

#include "pch.h"
#include "MainPage.xaml.h"
#include <http.h>
#include <robuffer.h>

using namespace FacePostProject;
using namespace concurrency;
using namespace Microsoft::WRL;
using namespace Platform;
using namespace Windows::Foundation;
using namespace Windows::Foundation::Collections;
using namespace Windows::UI::Xaml;
using namespace Windows::UI::Xaml::Controls;
using namespace Windows::UI::Xaml::Controls::Primitives;
using namespace Windows::UI::Xaml::Data;
using namespace Windows::UI::Xaml::Input;
using namespace Windows::UI::Xaml::Media;
using namespace Windows::UI::Xaml::Navigation;
using namespace Windows::Web::Http;
using namespace Windows::Web::Http::Filters;
using namespace Windows::Web::Http::Headers;
using namespace Windows::Storage::Streams;
using namespace Windows::UI::Core;

MainPage::MainPage()
{
	InitializeComponent();
}

void MainPage::Send_Click(Object^ sender, RoutedEventArgs^ e)
{
	// Load the image file a s a UWP StorageFile object
	Windows::Storage::StorageFile^ imageFile;
	imageFile = Windows::Storage::StorageFile::GetFileFromPathAsync("PATH TO SAVED FILE GOES HERE")->GetResults();

	// Get the image's file stream
	Windows::Storage::Streams::IRandomAccessStream^ stream;
	stream = imageFile->OpenAsync(Windows::Storage::FileAccessMode::Read)->GetResults();

	// New up an HttpClient and set the header with your API key
	HttpClient^ httpClient = ref new Windows::Web::Http::HttpClient();
	httpClient->DefaultRequestHeaders->Append("Ocp-Apim-Subscription-Key", "YOUR FACE API KEY GOES HERE");

	// Create stream content from the image file to send
	HttpStreamContent^ streamContent;
	streamContent = ref new Windows::Web::Http::HttpStreamContent(stream);
	streamContent->Headers->ContentLength = ref new Box<UINT64>(stream->Size);

	// Send image to API endpoint
	Windows::Web::Http::HttpRequestResult^ result;
	result = httpClient->TryPostAsync(ref new Uri("https://EASTUS2.cognitive.microsoft.com/face/v1.0/detect"),streamContent)->GetResults();

	if (result->Succeeded) 
	{
		String^ json;
	    json = result->ResponseMessage->Content->ReadAsStringAsync()->GetResults();
	}
}

void MainPage::Cancel_Click(Object^ sender, RoutedEventArgs^ e)
{
}

MainPage.xaml.h

#pragma once

#include "MainPage.g.h"

namespace FacePostProject
{
	public ref class MainPage sealed
	{
	public:
		MainPage();
	private:

		void Send_Click(Platform::Object^ sender, Windows::UI::Xaml::RoutedEventArgs^ e);
		void Cancel_Click(Platform::Object^ sender, Windows::UI::Xaml::RoutedEventArgs^ e);

		Concurrency::task<Windows::Storage::Streams::IRandomAccessStream^> GetFileStreamAsync(
			Windows::Storage::StorageFile^ file);
	};
}