HttpClient client = new HttpClient();
    var tokenEndpoint = "https://login.microsoftonline.com/testdir.onmicrosoft.com/oauth2/token";
    var body = "resource=www.graph.microsoft.com&client_id=" + App.ClientId + "&grant_type=password&username=" + UsernameEntry.Text + "&password=" + PasswordEntry.Text + "";
    var stringContent = new StringContent(body, Encoding.UTF8, "application/x-www-form-urlencoded");
    var result = await client.PostAsync(tokenEndpoint, stringContent).ContinueWith<string>(response => response.Result.Content.ReadAsStringAsync().Result);
    var jobject = JObject.Parse(result);
    App.AccessToken = jobject["access_token"].Value<string>();

tokenEndpoint = "https://login.microsoftonline.com/testdir.onmicrosoft.com/oauth2/authorize";
    body = "client_id=xxxx&response_type=code&redirect_uri=https://testapi.azurewebsites.net/";
    result = await client.PostAsync(tokenEndpoint, stringContent).ContinueWith<string>(response =>   response.Result.Content.ReadAsStringAsync().Result);
    jobject = JObject.Parse(result);