private IEnumerable<Person> StartSearch(SearchInfo searchInfo)
{
var token = cancellation.Token;
// Delay, to allow the user to continue typing.
Thread.Sleep(2000);
// A search triggered after this one might have occurred.
token.ThrowIfCancellationRequested();
MainWindowViewModel.SearchStatusProperty.SetValue(viewModel, "Searching");
var query = DataContext.QueryPeople();
if (!string.IsNullOrEmpty(searchInfo.GivenName))
query = query.Where(p => p.Firstname.StartsWith(searchInfo.GivenName, StringComparison.CurrentCultureIgnoreCase));
if (!string.IsNullOrEmpty(searchInfo.FamilyName))
query = query.Where(p => p.Surname.StartsWith(searchInfo.FamilyName, StringComparison.CurrentCultureIgnoreCase));
// Represents a delay in retrieving the information.
Thread.Sleep(1000);
token.ThrowIfCancellationRequested();
return query.ToArray();
}
public void DoSearch()
{
SearchInfo searchInfo = new SearchInfo();
MainWindowViewModel.SearchInfoProperties.SaveTo(searchInfo, viewModel);
if (string.IsNullOrEmpty(searchInfo.FamilyName) && string.IsNullOrEmpty(searchInfo.GivenName))
{
viewModel.PeopleResults.Clear();
return;
}
// Cancel any previous searches
cancellation.Cancel();
cancellation = new CancellationTokenSource();
searchTask = InitialTask();
MainWindowViewModel.SearchStatusProperty.SetValue(viewModel, "");
// Do the search off the UI thread.
searchTask = searchTask.ContinueWith<IEnumerable<Person>>(
previous => StartSearch(searchInfo),
cancellation.Token,
TaskContinuationOptions.OnlyOnRanToCompletion,
TaskScheduler.Default)
// Update the ViewModel with the search results on the UI thread.
.ContinueWith(
UpdateResults,
cancellation.Token,
TaskContinuationOptions.OnlyOnRanToCompletion,
TaskScheduler.FromCurrentSynchronizationContext());
}