title: how can I get refresh token
body: <p>i learn this code sample :<a href="https://github.com/Azure-Samples/active-directory-dotnet-graphapi-web" rel="noreferrer">https://github.com/Azure-Samples/active-directory-dotnet-graphapi-web</a> ,and yes ,i can get access token in AuthorizationCodeReceived : 
      AuthenticationHelper.token = result.AccessToken; </p>
  
  <p>but how do i get the refresh token ?result.RefreshToken is not available , then how do i use acquiretokenbyrefreshtoken function ? </p>
  
  <p><a href="https://msdn.microsoft.com/en-us/library/microsoft.identitymodel.clients.activedirectory.authenticationcontext.acquiretokenbyrefreshtoken.aspx" rel="noreferrer">https://msdn.microsoft.com/en-us/library/microsoft.identitymodel.clients.activedirectory.authenticationcontext.acquiretokenbyrefreshtoken.aspx</a></p>