I am using ASP.NET MVC 5 with OWIN.
I have done a lot of research and haven't found how to renew the access token using the refresh token.
My scenario is: The first time the user accesses my app, he or she grants access to the account I read the refresh token returned from the API. When the users come back to my app, I need to refresh the access token based on the "Refresh Token".
Could anybody provide some code?
Here is what I've achieved till now:
Startup.Auth.cs:
    var googleOAuth2AuthenticationOptions = new GoogleOAuth2AuthenticationOptions
    {
        Caption = "Google+",
        ClientId = Parameters.Instance.Authentication.oAuth.GooglePlus.ClientId,
        ClientSecret = Parameters.Instance.Authentication.oAuth.GooglePlus.ClientSecret,
        CallbackPath = new PathString("/oauth-login-return"),
        Provider = new GoogleOAuth2AuthenticationProvider
        {
            OnAuthenticated = async context =>
            {
                context.Identity.AddClaim(new Claim(ClaimTypes.Name, context.Identity.FindFirstValue(ClaimTypes.Name)));
                context.Identity.AddClaim(new Claim(ClaimTypes.Email, context.Identity.FindFirstValue(ClaimTypes.Email)));
                context.Identity.AddClaim(new Claim("picture", context.User.GetValue("picture").ToString()));
                context.Identity.AddClaim(new Claim("profile", context.User.GetValue("profile").ToString()));
                context.Identity.AddClaim(
                    new Claim(Parameters.Instance.Authentication.oAuth.GooglePlus.AccessTokenClaimType,
                        context.AccessToken));
            }
        }
    };
    googleOAuth2AuthenticationOptions.Scope.Add("https://www.googleapis.com/auth/plus.login");
    googleOAuth2AuthenticationOptions.Scope.Add("https://www.googleapis.com/auth/userinfo.email");
AuthenticationController:
[HttpPost]
[AllowAnonymous]
public ActionResult ExternalLogin(string provider, string returnUrl)
{
    RedirectIfAuthenticated();
    return new ChallengeResult(provider, Url.Content("~/oauth-login-callback"));
}
[ActionName("oauth-login-back")]
public async Task<ActionResult> ExternalLoginCallback(string returnUrl)
{
}
// Used for XSRF protection when adding external logins
private const string XsrfKey = "XsrfId";
private IAuthenticationManager AuthenticationManager
{
    get
    {
        return HttpContext.GetOwinContext().Authentication;
    }
}
private class ChallengeResult : HttpUnauthorizedResult
{
    public ChallengeResult(string provider, string redirectUri)
        : this(provider, redirectUri, null)
    {
    }
    private ChallengeResult(string provider, string redirectUri, string userId)
    {
        LoginProvider = provider;
        RedirectUri = redirectUri;
        UserId = userId;
    }
    private string LoginProvider { get; set; }
    private string RedirectUri { get; set; }
    private string UserId { get; set; }
    public override void ExecuteResult(ControllerContext context)
    {
        var properties = new AuthenticationProperties { RedirectUri = RedirectUri };
        if (UserId != null)
        {
            properties.Dictionary[XsrfKey] = UserId;
        }
        context.HttpContext.GetOwinContext().Authentication.Challenge(properties, LoginProvider);
    }
}

