Irfan TahirKheli Irfan TahirKheli - 1 year ago 211
ASP.NET (C#) Question

How to access users calendar list and events from google api using access token and refresh token

I already have obtained users access token from google api using oAuth2. Now i want to use this token to get user events/calendars. I have tried following code but it is not working.

Can anyone here help me with this please.

var urlBuilder = new System.Text.StringBuilder();


var httpWebRequest = HttpWebRequest.Create(urlBuilder.ToString()) as HttpWebRequest;

httpWebRequest.CookieContainer = new CookieContainer();
httpWebRequest.Headers["Authorization"] string.Format("Bearer {0}", data.access_token);
HttpWebResponse response = (HttpWebResponse)request.GetResponse();
Stream eventResponseStream = response.GetResponseStream();
StreamReader eventResponseStreamReader = new StreamReader(responseStream);
string eventsStr = eventResponseStreamReader.ReadToEnd();

Answer Source

I have found solution using Google.Apis.Calendar.v3, i am posting it here so may help someone else. Following is the code to get the events list when you have refresh token of a user:

First get new access token using the refresh token:

string postString = "client_id=yourclientid";
postString += "&client_secret=youclientsecret&refresh_token=userrefreshtoken";
postString += "&grant_type=refresh_token";
string url = "";

HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url.ToString());
request.Method = "POST";
request.ContentType = "application/x-www-form-urlencoded";
UTF8Encoding utfenc = new UTF8Encoding();
byte[] bytes = utfenc.GetBytes(postString);
Stream os = null;

    request.ContentLength = bytes.Length;
    os = request.GetRequestStream();
    os.Write(bytes, 0, bytes.Length);

    GoogleToken token = new GoogleToken();

    HttpWebResponse webResponse = (HttpWebResponse)request.GetResponse();
    Stream responseStream = webResponse.GetResponseStream();
    StreamReader responseStreamReader = new StreamReader(responseStream);
    string result = responseStreamReader.ReadToEnd();
    JavaScriptSerializer serializer = new JavaScriptSerializer();
    token = serializer.Deserialize<GoogleToken>(result);

Then use the toke and refresh token to create credentials.

var flow = new GoogleAuthorizationCodeFlow(new GoogleAuthorizationCodeFlow.Initializer
                ClientSecrets = new ClientSecrets
                    ClientId = yourclientid,
                    ClientSecret = yourclientsecret
                Scopes = new[] { CalendarService.Scope.Calendar }

            var credential = new UserCredential(flow, Environment.UserName, new TokenResponse
                AccessToken = token.access_token,
                RefreshToken = userrefreshtoke

            CalendarService service = new CalendarService(new BaseClientService.Initializer()
                HttpClientInitializer = credential,
                ApplicationName = "application name",
            var list = service.CalendarList.List().Execute().Items;
            foreach (var c in list)
                var events = service.Events.List(c.Id).Execute().Items.Where(i => i.Start.DateTime >= DateTime.Now).ToList();
                foreach (var e in events)

GoogleToken class:

 public class GoogleToken
        public string access_token { get; set; }
        public string token_type { get; set; }
        public string expires_in { get; set; }       
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