private async Task GetSelectedAnswerAsync()
{
var selectedQuestion = GetSelectedQuestion();
response = !string.IsNullOrEmpty(userName) && selectedQuestion != null
? await service.GetResponseForSurveyAsync(selectedQuestion.Id, userName)
: null;
SetSelectedAnswer();
}
/// <summary>
/// Constructor
/// </summary>
/// <param name="surveyService">Service to retrieve data from</param>
/// <param name="dependencyService">Service Locator</param>
public MainViewModel(ISurveyQuestionService surveyService, IDependencyService dependencyService)
{
this.surveyService = surveyService;
this.dependencyService = dependencyService;
// Setup our collection of questions. This is an async collection populated by our
// survey service. The single constructor parameter is an async function to load the data.
questions = new RefreshingCollection <SurveyQuestion>(surveyService.GetQuestionsAsync)
{
// What to do if the refresh fails..
RefreshFailed = async(s, ex) =>
{
IsLoadingData = false;
await Task.Delay(1000); // get out of the binding.
await dependencyService.Get <IMessageVisualizerService>()
.ShowMessage("Error", "Failed to get questions: " + ex.Message, "OK");
},
// Called before a refresh occurs to save off the current selection.
BeforeRefresh = s =>
{
IsLoadingData = true;
return(SelectedQuestion);
},
// Called after a refresh completes successfully; restores the selection.
AfterRefresh = (s, sq) =>
{
IsLoadingData = false;
if (sq == null)
{
sq = questions.FirstOrDefault();
}
if (sq != null)
{
var newSelection = questions.SingleOrDefault(q => q.Id == ((SurveyQuestion)sq).Id);
SelectedQuestion = newSelection;
}
}
};
// Setup the collection of answers; this is refreshed each time the
// selected question changes.
answers = new RefreshingCollection <AnswerViewModel>(async() =>
{
IsLoadingData = true;
try
{
var id = SelectedQuestion.Id;
string [] choices = SelectedQuestion.Answers.Split('|');
if (HasName)
{
response = await surveyService.GetResponseForSurveyAsync(id, Name);
}
else
{
response = null;
}
int answerIndex = response == null ? -1 : response.ResponseIndex;
return(Enumerable.Range(0, choices.Length)
.Select(i => new AnswerViewModel(choices [i], i)
{
IsSelected = answerIndex == i
}));
}
catch (Exception ex)
{
await dependencyService.Get <IMessageVisualizerService>()
.ShowMessage("Error", "Failed to get answers/responses: " + ex.Message, "OK");
return(null);
}
finally
{
IsLoadingData = false;
}
});
}
