ReturnUrl Parameter Is Null After Redirect

[corydeppen]

I'm not sure if it's safe to assume that many folks will be integrating this library into MVC projects that contain an AccountsController from the default MVC template, but I noticed that the returnUrl parameter of the ExternalLoginCallback method is null after the redirect. Since the returnUrl parameter is actually inside the state parameter that Google passes back, I had to add the following snippet:

GoogleOAuth2Client.RewriteRequest();

// Pull the returnUrl from the rewritten request,
// since it was originally packed in the state parameter.
var url = Request.QueryString["ReturnUrl"];
if (string.IsNullOrEmpty(returnUrl) && url != null)
{
    returnUrl = url;
}

OAuthWebSecurity.VerifyAuthentication(....)

This may be something others find useful and might be helpful to include in the Usage section of the readme.

[mattjohnsonpint]

Good point. The docs should clarify that anything packed into the state parameter are now found directly on the querystring.

[mattjohnsonpint]

Updated the readme. And thanks!