oauth API with the Access Token to retrieve some of users information.

private async void getgoogleplususerdataSer(string access_token)
{
    try
    {
        HttpClient client = new HttpClient();
        var urlProfile = "https://www.googleapis.com/oauth2/v1/userinfo?access_token=" + access_token;

        client.CancelPendingRequests();
        HttpResponseMessage output = await client.GetAsync(urlProfile);

        if (output.IsSuccessStatusCode)
        {
            string outputData = await output.Content.ReadAsStringAsync();
            GoogleUserOutputData serStatus = JsonConvert.DeserializeObject<GoogleUserOutputData>(outputData);

            if (serStatus != null)
            {
                 // You will get the user information here.
            }
        }
    }
    catch (Exception ex)
    { 
         //catching the exception
    }
}

public class GoogleUserOutputData
{
    public string id { get; set; }
    public string name { get; set; }
    public string given_name { get; set; }
    public string email { get; set; }
    public string picture { get; set; }
}