ViewModel
public class MyViewModel:ReactiveObject, IRoutableViewModel{
private ReactiveList<string> _appExtensions;
public MyViewModel(IScreen screen){
HostScreen = screen;
AppExtensions = new ReactiveList<string>();
GetApplicationExtensions =
ReactiveCommand.CreateAsyncTask(x => _schemaService.GetApplicationExtensions()); // returns a Task<IEnumerable<string>>
GetApplicationExtensions
.ObserveOn(RxApp.MainThreadScheduler)
.SubscribeOn(RxApp.TaskpoolScheduler)
.Subscribe(p =>
{
using (_appExtensions.SuppressChangeNotifications())
{
_appExtensions.Clear();
_appExtensions.AddRange(p);
}
});
GetApplicationExtensions.ThrownExceptions.Subscribe(
ex => Console.WriteLine("Error during fetching of application extensions! Err: {0}", ex.Message));
}
// bound to a ListBox
public ReactiveList<string> AppExtensions
{
get { return _appExtensions; }
set { this.RaiseAndSetIfChanged(ref _appExtensions, value); }
}
public ReactiveCommand<IEnumerable<string>> GetApplicationExtensions { get; protected set; }
}
and the View has a <Button Command="{Binding GetApplicationExtensions}"></Button>.
implentation of GetApplicationExtensions
public async Task<IEnumerable<string>> GetApplicationExtensions()
{
IEnumerable<string> extensions = null;
using (var client = new HttpClient())
{
client.BaseAddress = BaseAddress;
client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", _accessToken);
var response = await client.GetAsync("applications");
if (response.IsSuccessStatusCode)
{
var json = await response.Content.ReadAsStringAsync();
extensions = JsonConvert.DeserializeObject<IEnumerable<string>>(json);
}
}
return extensions;
}
From everything I've read about ReactiveUI and all the examples I've seen (althought there are extremely few for the new 6.0+ versions), this should make my async call (which makes an async HTTP request via HttpClient) run on a background thread and update a ListBox in my view when the results are returned from it. However, this is not the case - the UI gets locked up for the duration of the async call. What am I doing wrong?
UPDATE
If I wrapped my HTTP call in a Task then everything worked as intended - the UI did not hang up at all. So the new implementation of my service call is this:
public Task<IEnumerable<string>> GetApplicationExtensions()
{
var extensionsTask = Task.Factory.StartNew(async () =>
{
IEnumerable<string> extensions = null;
using (var client = new HttpClient())
{
client.BaseAddress = BaseAddress;
client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", _accessToken);
var response = await client.GetAsync("applications");
if (response.IsSuccessStatusCode)
{
var json = await response.Content.ReadAsStringAsync();
extensions = JsonConvert.DeserializeObject<IEnumerable<string>>(json);
}
}
return extensions;
}
return extensionsTask.Result;
}
Also, with this change to my async service call, I could remove the ObserveOn and SubscribeOn from my ReactiveCommand like @PaulBetts suggessted. So my ReactiveCommand implementation in my view model's constructor became this:
GetApplicationExtensions =
ReactiveCommand.CreateAsyncTask(x => _schemaService.GetApplicationExtensions()); // returns a Task<IEnumerable<string>>
GetApplicationExtensions
.Subscribe(p =>
{
using (_appExtensions.SuppressChangeNotifications())
{
_appExtensions.Clear();
_appExtensions.AddRange(p);
}
});
