I'm trying to call LoadPickerData method to load the result in a Picker using async/await from the a ViewModel. I get the following error:
Error
System.AggregateException
Message=One or more errors occurred. (A task was canceled.)
Source=mscorlib
StackTrace:
at System.Threading.Tasks.Task.ThrowIfExceptional (System.Boolean includeTaskCanceledExceptions) [0x00011] in /Users/builder/jenkins/workspace/archive-mono/2019-08/android/release/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/Task.cs:2027
at System.Threading.Tasks.Task`1[TResult].GetResultCore (System.Boolean waitCompletionNotification) [0x0002b] in /Users/builder/jenkins/workspace/archive-mono/2019-08/android/release/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/Future.cs:496
at System.Threading.Tasks.Task`1[TResult].get_Result () [0x00000] in /Users/builder/jenkins/workspace/archive-mono/2019-08/android/release/external/corert/src/System.Private.CoreLib/src/System/Threading/Tasks/Future.cs:466
at EmployeeApp.Helpers.ConnectivityHelper.CheckConnectivity () [0x00049] in F:\Workspace\BajaDev\MPA\_Project\EmployeeApp\Helpers\ConnectivityHelper.cs:34
at EmployeeApp.Helpers.ConnectivityHelper.get_IsConnected () [0x00000] in F:\Workspace\BajaDev\MPA\_Project\EmployeeApp\Helpers\ConnectivityHelper.cs:21
at EmployeeApp.ViewModels.BaseViewModel.get_ServiceAreaStore () [0x00000] in F:\Workspace\BajaDev\MPA\_Project\EmployeeApp\ViewModels\BaseViewModel.cs:27
at EmployeeApp.ViewModels.MailboxViewModel.GetPickerServiceArea () [0x0000f] in F:\Workspace\BajaDev\MPA\_Project\EmployeeApp\ViewModels\MailboxViewModel.cs:60
at EmployeeApp.MailboxPage.LoadPickerData () [0x0002b] in F:\Workspace\BajaDev\MPA\_Project\EmployeeApp\Views\MailBoxPage.xaml.cs:70
at EmployeeApp.MailboxPage.OnAppearing () [0x0002c] in F:\Workspace\BajaDev\MPA\_Project\EmployeeApp\Views\MailBoxPage.xaml.cs:31
at System.Runtime.CompilerServices.AsyncMethodBuilderCore+<>c.<ThrowAsync>b__7_0 (System.Object state) [0x00000] in /Users/builder/jenkins/workspace/archive-mono/2019-08/android/release/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/AsyncMethodBuilder.cs:1021
at Android.App.SyncContext+<>c__DisplayClass2_0.<Post>b__0 () [0x00000] in <06692e0cad5848598a0f46942a89e99f>:0
at Java.Lang.Thread+RunnableImplementor.Run () [0x00008] in <06692e0cad5848598a0f46942a89e99f>:0
at Java.Lang.IRunnableInvoker.n_Run (System.IntPtr jnienv, System.IntPtr native__this) [0x00009] in <06692e0cad5848598a0f46942a89e99f>:0
at (wrapper dynamic-method) Android.Runtime.DynamicMethodNameCounter.44(intptr,intptr)
I'm trying to load the result of a GET request in a picker, but when I start the app the first time, it does not and I get the previous exception and the second time I run it I no longer get that error. I looked for why and I was making the call of an asynchronous method in a constructor and that is bad code, I changed it to an OnAppearing () method but still that exception keeps coming out and I don't have idea the why yet
MailboxPage.xaml.cs
public MailboxPage()
{
InitializeComponent();
BindingContext = viewModel = new MailboxViewModel();
}
protected override async void OnAppearing()
{
base.OnAppearing();
await LoadPickerData();
}
private async Task<IEnumerable<ServiceArea>> LoadPickerData()
{
var vm = new MailboxViewModel();
var servicesareas = await vm.GetPickerServiceArea();
try
{
ServiceAreaPicker.ItemsSource = servicesareas.ToList();
ServiceAreaPicker.ItemDisplayBinding = new Binding("Name");
}
catch(AggregateException ae)
{
foreach (var e in ae.Flatten().InnerExceptions)
{
Debug.WriteLine($"{e.GetType().FullName} { e.Message}");
}
}
return servicesareas;
}
MailboxViewModel.cs
public async Task<IEnumerable<ServiceArea>> GetPickerServiceArea()
{
try
{
PickerItems = await ServiceAreaStore.GetPickerItemsAsync(true);
foreach (var item in PickerItems)
Items.Add(item);
}
catch (AggregateException ae)
{
foreach (var e in ae.Flatten().InnerExceptions)
{
Debug.WriteLine($"{e.GetType().FullName} { e.Message}");
}
}
return PickerItems;
}
ServiceAreaStoreAPI.cs
public async Task<IEnumerable<ServiceArea>> GetPickerItemsAsync(bool forceRefresh = false)
{
if (forceRefresh)
{
var json = await Client.GetStringAsync($"api/servicearea");
Servicesareas = await Task.Run(() => JsonConvert.DeserializeObject<IEnumerable<ServiceArea>>(json));
try
{
var success = LocalDatabase.AddItemsAsync(Servicesareas);
if (!success.Result)
{
//Log de fallo en la insercion de datos.
}
}
catch(AggregateException ae)
{
foreach (var e in ae.Flatten().InnerExceptions)
{
Debug.WriteLine($"{e.GetType().FullName} { e.Message}");
}
}
}
return Servicesareas;
}
In your ServiceAreaStoreAPI
, you don't await a task which might be causing your issue since it'll continue on and return a canceled result.
var success = LocalDatabase.AddItemsAsync(Servicesareas);