Develop Reference

GetToastCollectionManager crash

I already have Toast Notifications working, but I need to create a collection for them.
Following the code example in : https://learn.microsoft.com/en-us/windows/apps/design/shell/tiles-and-notifications/toast-collections
I get a crash on the GetToastCollectionManager call.
System.Exception
HResult=0x80070490
Message=Element not found. (0x80070490)
Source=<Cannot evaluate the exception source>
StackTrace:
<Cannot evaluate the exception stack trace>
This exception was originally thrown at this call stack:
WpfApp1.MainWindow.CreateToastCollection() in MainWindow.xaml.cs
I'm not sure if I'm missing something obvious , but I cannot find examples or tutorials on Toast Notifications.
Any Ideas ?
public async void CreateToastCollection()
{
ToastNotificationManagerForUser defaultManager = ToastNotificationManager.GetDefault();
ToastCollectionManager collectionManager = defaultManager.GetToastCollectionManager();
string displayName = "Is Potato";
string launchArg = "NavigateToPotato";
System.Uri iconURI = new System.Uri("ms-appx:///Assets/icon.png");
ToastCollection licensingManagerToastCollection = new ToastCollection(
"MyToastCollection",
displayName,
launchArg,
iconURI);
// Calls the platform to create the collection
await collectionManager.SaveToastCollectionAsync(licensingManagerToastCollection);
}

Why is my stack trace being truncated?

I have a partial-trust AppDomain within which I run a full-trust debugging window. Using PermissionSetAttribute to get permissions I can create the window and do plenty of things with it, but sometimes a SecurityException will be thrown during data binding.
One easily reproducible case throws this: Property accessor 'Namespace' on object 'System.RuntimeType' threw the following exception:'Request failed.'. Digging into the exception I can see that it was thrown when full trust was demanded.
No problem, the debug window assembly has full trust and I simply need to assert it. But when I look at the stack trace of the inner SecurityException I see this:
at System.Security.CodeAccessSecurityEngine.Check(Object demand, StackCrawlMark& stackMark, Boolean isPermSet)
at System.Security.CodeAccessSecurityEngine.Check(PermissionSet permSet, StackCrawlMark& stackMark)
at System.Security.PermissionSet.Demand()
at System.SecurityUtils.DemandGrantSet(Assembly assembly)
at System.SecurityUtils.DemandReflectionAccess(Type type)
at System.SecurityUtils.MethodInfoInvoke(MethodInfo method, Object target, Object[] args)
at System.ComponentModel.ReflectPropertyDescriptor.GetValue(Object component)
It ends right there, at ReflectPropertyDescriptor.GetValue.
In Visual Studio's Call Stack window I can see ReflectPropertyDescriptor.GetValue at the very tip of the stack. That stack goes all the way back to the creation of the debug window and the security assert I performed there, which is exactly what I want.
Why has the stack been split in two like this? How can I stop it from happening?
I'm using .Net 4.0 security (i.e. Level 2).

This isn't that odd. Visual studio's call stack is showing you the method which you were at when the current exception was thrown . The InnerException shows the callstack of where the inner exception exception occurred. After the inner exception was thrown, it propagated up the callstack thus unwinding it until it got to ReflectPropertyDescriptor.GetValue. At that point, it was caught in a catch block and set as the inner exception of a new exception which then thrown and bubbled all the way up. So the call stack for the second exception begins at the point it was thrown (i.e. ReflectPropertyDescriptor.GetValue)
Here's a simple example which reproduces this.
namespace Exceptions
{
class ExceptionTester
{
public void Run()
{
ThrowSecondException();
}
public void DoSomething()
{
DoMore();
}
public void DoMore()
{
ThrowFirstException();
}
public void ThrowFirstException()
{
throw new FooException();
}
public void ThrowSecondException()
{
try
{
DoSomething();
}
catch (FooException e)
{
throw new BarException("derp", e);
}
}
}
class FooException : Exception
{
}
class BarException : Exception
{
public BarException(string msg, Exception inner) : base(msg, inner)
{
}
}
class Program
{
static void Main(string[] args)
{
var tester = new ExceptionTester();
tester.Run();
}
}
}
When the second exception of type BarException is thrown, you'll notice that visual studio has ThrowSecondException at the top of the call stack because that is where BarException was thrown. However, when you dig into BarException's InnerException and look at FooException's call stack, it'll show you where FooException was thrown (ThrowFirstException()).

odata unknown function cast

I have a web api project that host my models, in my .net application, when I query this :
static void TitleById(MoviesService.Container container, short id)
{
try
{
MoviesService.Title title = container.Title.Where(w => w.Id == id).SingleOrDefault();
if (title != null)
{
DisplayTitle(title);
}
}
catch (Exception e)
{
Console.WriteLine(e.Message);
}
}
the problem is not with the query, it's from id variable. the id variable is of the short type not an int. here is the exception message :
<?xml version="1.0" encoding="utf-8"?>
<m:error xmlns:m="http://schemas.microsoft.com/ado/2007/08/dataservices/metadata">
<m:code />
<m:message xml:lang="en-US">An error has occurred.</m:message>
<m:innererror>
<m:message>Unknown function 'cast'.</m:message>
<m:type>System.NotImplementedException</m:type>
<m:stacktrace> at System.Web.Http.ApiController.<InvokeActionWithExceptionFilters>d__1.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at System.Web.Http.Dispatcher.HttpControllerDispatcher.<SendAsync>d__0.MoveNext()</m:stacktrace>
</m:innererror>
</m:error>
and here is odata url :
"GET http://localhost:21401/odata/Title()?$filter=cast(Id,'Edm.Int32') eq 3&$top=2"
well, the type of Id property in my entites is short. how can I pass it to the query?
Thanks, If I have to bring more information, please tell me.

I found that cast is not implemented in FilterBinder.BindSingleValueFunctionCallNode in source code:
https://aspnetwebstack.codeplex.com/SourceControl/latest#src/System.Web.Http.OData/OData/Query/Expressions/FilterBinder.cs
One of the way to solve it is to download the code and implement yourself.

System.AggregateException on Socket.EndAccept with TaskFactory.FromAsync

I am working with async operations with sockets (.Net 4 - VS 2010 SP1) and all seems to be working okay. However, after write and run an automated test, it pass green but displays an exception message:
---- UNHANDLED EXCEPTION ----
Thread Name: <No Name>
System.AggregateException: A Task's exception(s) were not observed either by Waiting on the Task or accessing its Exception property. As a result, the unobserved exception was rethrown by the finalizer thread. ---> System.ObjectDisposedException: Cannot access a disposed object.
Object name: 'System.Net.Sockets.Socket'.
at System.Net.Sockets.Socket.EndAccept(IAsyncResult asyncResult)
at P2PNet.Listener.<ListenForConnections>b__0(IAsyncResult r) in C:\Users\lucas.ontivero\Documents\Visual Studio 2010\Projects\P2PNet\P2PNet\Listener.cs:line 76
at System.Threading.Tasks.TaskFactory`1.FromAsyncCoreLogic(IAsyncResult iar, Func`2 endMethod, TaskCompletionSource`1 tcs)
--- End of inner exception stack trace ---
at System.Threading.Tasks.TaskExceptionHolder.Finalize()
---> (Inner Exception #0) System.ObjectDisposedException: Cannot access a disposed object.
Object name: 'System.Net.Sockets.Socket'.
at System.Net.Sockets.Socket.EndAccept(IAsyncResult asyncResult)
at P2PNet.Listener.<ListenForConnections>b__0(IAsyncResult r) in C:\Users\lucas.ontivero\Documents\Visual Studio 2010\Projects\P2PNet\P2PNet\Listener.cs:line 76
at System.Threading.Tasks.TaskFactory`1.FromAsyncCoreLogic(IAsyncResult iar, Func`2 endMethod, TaskCompletionSource`1 tcs)<---
I know what that exception means, it means the socket was closed before the EndAccept method was called. I have no problems with that, what I really don´t know is how to prevent that exception in an elegant way. This is my code:
private void ListenForConnections()
{
try
{
Task.Factory.FromAsync<Socket>(_listener.BeginAccept, _listener.EndAccept, _listener)
.ContinueWith(task =>
{
if (task.IsFaulted) return;
ListenForConnections();
var newSocket = task.Result;
RaiseClientConnectedEvent(new ConnectionEventArgs(newSocket));
}, TaskContinuationOptions.OnlyOnRanToCompletion);
}
catch (ObjectDisposedException)
{
}
I´ve tried with the line:
if (task.IsFaulted) return;
and also with:
.ContinueWith(task=>{}, TaskContinuation.OnlyOnFault);
But the exception is thrown anyway. Which is the way to prevent the exception?
Thank you!

Your line:
if (task.IsFaulted) return;
Is returning not faulted because you are checking the continuation task's status, not the preceding task. Change it to this:
private void ListenForConnections() {
Task<Socket> listentask = Task.Factory.FromAsync<Socket>(_listener.BeginAccept, _listener.EndAccept, _listener);
listentask.ContinueWith(task => {
if (listentask.IsFaulted) {
//observe exception
Exception exception = listentask.Exception;
return;
}
ListenForConnections();
var newSocket = listentask.Result;
RaiseClientConnectedEvent(new ConnectionEventArgs(newSocket));
});
//don't forget to start it
listentask.Start();
}

You need to observe the exception by reading the Exception property. Do that inside of your continuation.

What causes a System.Runtime.InteropServices.COMException at BackgroundAudioPlayer.get_Position()?

Sometimes I'm getting an exception when trying to get the position of the BackgroundAudioPlayer.Instance. It's happening very rarely, but I've been able to get a StackTrace. The strange thing is, this code is executed every second while playing a track. What could be the cause of this error?
I'm getting this StackTrace.
System.SystemException: HRESULT = 0xC00D36C4 ---> System.Runtime.InteropServices.COMException: Exception from HRESULT: 0xC00D36C4 at
Microsoft.Phone.BackgroundAudio.Interop.IAudioPlaybackManager.get_CurrentPosition() at
Microsoft.Phone.BackgroundAudio.BackgroundAudioPlayer.get_Position() --- End of inner exception stack trace --- at
Microsoft.Phone.BackgroundAudio.BackgroundAudioPlayer.get_Position() at
MC.PodCast.Common.ViewModel.PlayerViewModel.UpdateTrackPosition() at
MC.PodCast.Common.ViewModel.PlayerViewModel.ReactToBackgroundAudioPlayer() at
MC.PodCast.Common.ViewModel.PlayerViewModel.Initialize() at
MC.PodCast.Common.ViewModel.PlayerViewModel.<<get_InitializeCommand>b__5>d__6.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.CompilerServices.AsyncMethodBuilderCore.<ThrowAsync>b__0(Object state)
Of course the code I'm using is just plain simple.
public void UpdateTrackPosition()
{
if (_backgroundAudioPlayer != null && _backgroundAudioPlayer.Track != null)
{
Position = _backgroundAudioPlayer.Position;
}
else
{
Position = null;
}
}

That code is linked to MF_MEDIA_ENGINE_ERR_SRC_NOT_SUPPORTED but I'm guessing that you do have sound.
I have found that the BackgroundAudioPlyer can be very weird. I wrap most of my calls with a "Safe" extension method.
Example
public static PlayState PlayerStateSafe(this BackgroundAudioPlayer source)
{
PlayState state;
try
{
state = source.PlayerState;
}
catch (InvalidOperationException)
{
state = PlayState.Unknown;
}
return state;
}