C# - How do I retrieve google cloud printers with OAuth2 Access Token?

Question

I have already got printers list and submitted a printer job to Google Cloud Print through this code "Google Cloud Print using C#" but I can not use Google's passwords of my customers for access theirs printers.

Now I am implementing the oauth2 authentication and I have gained the access to Calendar and to Google Cloud Print of a testing account but now I do not understand how to retrieve the list of printers and how post a printer's job with this authorization token.

For oauth2 i have download this example and works very well "https://github.com/nanovazquez/google-calendar-sample".

For have rights to Google Cloud Print just add "https://www.googleapis.com/auth/cloudprint" at _scopes member.

using System.Web;
using DotNetOpenAuth.OAuth2;
using Google.Apis.Authentication.OAuth2;
using Google.Apis.Authentication.OAuth2.DotNetOpenAuth;
using Google.Apis.Calendar.v3;
using Google.Apis.Util;

namespace GoogleApiUtils
{
    public static class GoogleAuthorizationHelper
    {
        private static string _clientId = ConfigurationManager.AppSettings["ClientId"];
        private static string _clientSecret = ConfigurationManager.AppSettings["ClientSecret"];
        private static string _redirectUri = ConfigurationManager.AppSettings["RedirectUri"];
        private static string[] _scopes = new[] { CalendarService.Scopes.Calendar.GetStringValue(), "https://www.googleapis.com/auth/cloudprint" };

...

Does anyone have some advice to give me?

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I have resolved. I have created a small project so anyone can see how I have solved my question and maybe someone could give a better solution. Now I am going to share it. — AppAndTouch

AppAndTouch AppAndTouch · Accepted Answer · 2014-09-18T16:36:50

I made a small C# MVC project. I retrieved the OAuth2 Access Token and I used it for get list of Google Cloud Printer. I do not know if there are other method for do that. I hope this could help someone.

My big problem was been how refresh access token when it expires. This is my solution:

    public async Task<ActionResult> PrintersListAsync(CancellationToken cancellationToken)
    {           
        cancellationToken.ThrowIfCancellationRequested();

        List<CloudPrinter> model = new List<CloudPrinter>();

        try
        {
             ViewBag.Message = "Your printers.";

            var result = await new AuthorizationCodeMvcApp(this, new AppAuthFlowMetadata()).AuthorizeAsync(cancellationToken);

            if (result.Credential == null)
            {
                // Open Google page for authorization
                return new RedirectResult(result.RedirectUri);
            }

            //Check if token is expired
            if (result.Credential.Token.IsExpired(Google.Apis.Util.SystemClock.Default)) {
                //renew token
                Boolean tokenRefreshed = await result.Credential.RefreshTokenAsync(cancellationToken);

                if (!tokenRefreshed)
                {                       
                    //Refresh token failed!
                    return new RedirectResult(result.RedirectUri);
                }
            }

            //Ok, now we have rights to access to user printers
            GoogleCloudPrint cloudPrint = new GoogleCloudPrint(result.Credential, String.Empty);

            //Get printers list
            var printers = cloudPrint.Printers;
            if (printers.success)
            {
                model = printers.printers;
            }

            return View(model);
        }
        catch (Exception ex)
        {
            ViewBag.Message = "Exception: " + ex.Message;

            return View(model); 
        }           
    }

Link to C# MVC project

Any improvement is appreciated.

C# - How do I retrieve google cloud printers with OAuth2 Access Token?

1 Answers