title: C++/CX: Platform::String vs. std::wstring
body: <p>It seems that C++/CX does not have a StringBuilder class, or equivalent, so I take it we are to be using STL for this?</p>
  
  <p>This is my <em>very first</em> C++/CX app.  The user enters some text in a TextBox, hits the ENTER button, and the text is appended to a TextBlock "console".  This code does work, but what's the best practice?</p>
  
  <pre><code>public ref class MainPage sealed
  {
  public:
      MainPage();
  
  protected:
      virtual void OnNavigatedTo(Windows::UI::Xaml::Navigation::NavigationEventArgs^ e) override;
  private:
      std::wstring _commandLine;
      std::wstring _consoleText;
      void Button_Click(Platform::Object^ sender, Windows::UI::Xaml::RoutedEventArgs^ e);
  };
  </code></pre>
  
  <p>...</p>
  
  <pre><code>void HelloConsole::MainPage::Button_Click(Platform::Object^ sender, Windows::UI::Xaml::RoutedEventArgs^ e)
  {
      this-&gt;_commandLine = this-&gt;InputLine-&gt;Text-&gt;Data();
      this-&gt;_commandLine.append(L"\n");
      this-&gt;_consoleText += this-&gt;_commandLine;
      this-&gt;InputLine-&gt;Text = "";
      this-&gt;OutputConsole-&gt;Text = ref new Platform::String(_consoleText.c_str());
  }
  </code></pre>