Async always WaitingForActivation

Question

I am trying to figure out what the async  amp  await keywords are all about  however the output isn t what I m expecting   The console application is as follows   class Program       static void Main string   args                Console WriteLine  Foo called            var result   Foo 5            while  result Status    TaskStatus RanToCompletion                        Console WriteLine  Thread ID   0   Status   1    Thread CurrentThread ManagedThreadId  result Status               Task Delay 100  Wait                       Console WriteLine  Result   0    result Result           Console WriteLine  Finished             Console ReadKey true              private static async Task lt string gt  Foo int seconds                return await Task Run      gt                                for  int i   0  i  lt  seconds  i                                          Console WriteLine  Thread ID   0   second  1     Thread CurrentThread ManagedThreadId  i                       Task Delay TimeSpan FromSeconds 1   Wait                                       return  Foo Completed                              The output is   Foo called Thread ID  10  Status  WaitingForActivation Thread ID  6  second 0  Thread ID  10  Status  WaitingForActivation Thread ID  10  Status  WaitingForActivation Thread ID  10  Status  WaitingForActivation Thread ID  10  Status  WaitingForActivation Thread ID  10  Status  WaitingForActivation Thread ID  10  Status  WaitingForActivation Thread ID  10  Status  WaitingForActivation Thread ID  10  Status  WaitingForActivation Thread ID  6  second 1  Thread ID  10  Status  WaitingForActivation Thread ID  10  Status  WaitingForActivation Thread ID  10  Status  WaitingForActivation Thread ID  10  Status  WaitingForActivation Thread ID  10  Status  WaitingForActivation Thread ID  10  Status  WaitingForActivation Thread ID  10  Status  WaitingForActivation Thread ID  10  Status  WaitingForActivation Thread ID  10  Status  WaitingForActivation Thread ID  6  second 2  Thread ID  10  Status  WaitingForActivation Thread ID  10  Status  WaitingForActivation Thread ID  10  Status  WaitingForActivation Thread ID  10  Status  WaitingForActivation Thread ID  10  Status  WaitingForActivation Thread ID  10  Status  WaitingForActivation Thread ID  10  Status  WaitingForActivation Thread ID  10  Status  WaitingForActivation Thread ID  10  Status  WaitingForActivation Thread ID  10  Status  WaitingForActivation Thread ID  6  second 3  Thread ID  10  Status  WaitingForActivation Thread ID  10  Status  WaitingForActivation Thread ID  10  Status  WaitingForActivation Thread ID  10  Status  WaitingForActivation Thread ID  10  Status  WaitingForActivation Thread ID  10  Status  WaitingForActivation Thread ID  10  Status  WaitingForActivation Thread ID  10  Status  WaitingForActivation Thread ID  10  Status  WaitingForActivation Thread ID  6  second 4  Thread ID  10  Status  WaitingForActivation Thread ID  10  Status  WaitingForActivation Thread ID  10  Status  WaitingForActivation Thread ID  10  Status  WaitingForActivation Thread ID  10  Status  WaitingForActivation Thread ID  10  Status  WaitingForActivation Thread ID  10  Status  WaitingForActivation Thread ID  10  Status  WaitingForActivation Thread ID  10  Status  WaitingForActivation Result  Foo Completed  Finished     I was expecting to see the status changing from WaitingForActivation once the method is started   How can it stay in this state and be active

User · Answer

I overcome this issue with if anybody interested   In myMain method i called my readasync method like  Dispatcher BeginInvoke new ThreadStart      gt  ReadData        Everything is fine for me now

User · Answer

I had the same problem  The answers got me on the right track  So the problem is that  functions marked with async don t return a task of the function itself as expected  but another continuation task of the function    So its the  await and  async  keywords that screws thing up  The simplest solution then is simply to remove them  Then it works as expected  As in   static void Main string   args        Console WriteLine  Foo called        var result   Foo 5        while  result Status    TaskStatus RanToCompletion                Console WriteLine  Thread ID   0   Status   1    Thread CurrentThread ManagedThreadId  result Status           Task Delay 100  Wait               Console WriteLine  Result   0    result Result       Console WriteLine  Finished         Console ReadKey true      private static Task lt string gt  Foo int seconds        return Task Run      gt                for  int i   0  i  lt  seconds  i                          Console WriteLine  Thread ID   0   second  1     Thread CurrentThread ManagedThreadId  i               Task Delay TimeSpan FromSeconds 1   Wait                       return  Foo Completed                Which outputs   Foo called Thread ID  1  Status  WaitingToRun Thread ID  3  second 0  Thread ID  1  Status  Running Thread ID  1  Status  Running Thread ID  1  Status  Running Thread ID  1  Status  Running Thread ID  1  Status  Running Thread ID  1  Status  Running Thread ID  1  Status  Running Thread ID  1  Status  Running Thread ID  1  Status  Running Thread ID  3  second 1  Thread ID  1  Status  Running Thread ID  1  Status  Running Thread ID  1  Status  Running Thread ID  1  Status  Running Thread ID  1  Status  Running Thread ID  1  Status  Running Thread ID  1  Status  Running Thread ID  1  Status  Running Thread ID  1  Status  Running Thread ID  3  second 2  Thread ID  1  Status  Running Thread ID  1  Status  Running Thread ID  1  Status  Running Thread ID  1  Status  Running Thread ID  1  Status  Running Thread ID  1  Status  Running Thread ID  1  Status  Running Thread ID  1  Status  Running Thread ID  1  Status  Running Thread ID  3  second 3  Thread ID  1  Status  Running Thread ID  1  Status  Running Thread ID  1  Status  Running Thread ID  1  Status  Running Thread ID  1  Status  Running Thread ID  1  Status  Running Thread ID  1  Status  Running Thread ID  1  Status  Running Thread ID  1  Status  Running Thread ID  3  second 4  Thread ID  1  Status  Running Thread ID  1  Status  Running Thread ID  1  Status  Running Thread ID  1  Status  Running Thread ID  1  Status  Running Thread ID  1  Status  Running Thread ID  1  Status  Running Thread ID  1  Status  Running Thread ID  1  Status  Running Thread ID  1  Status  Running Result  Foo Completed  Finished

User · Answer

this code seems to have address the issue for me   it comes for a streaming class  ergo some of the nomenclature         lt summary gt  Reference to the awaiting task   lt  summary gt       lt value gt  The awaiting task   lt  value gt  Protected ReadOnly Property AwaitingTask As Threading Tasks Task       lt summary gt  Reference to the Action task  this task status undergoes changes   lt  summary gt  Protected ReadOnly Property ActionTask As Threading Tasks Task       lt summary gt  Reference to the cancellation source   lt  summary gt  Protected ReadOnly Property TaskCancellationSource As Threading CancellationTokenSource       lt summary gt  Starts the action task   lt  summary gt       lt param name  taskAction  gt  The action to stream the entities  which calls                                lt see cref  StreamEvents Of T  IEnumerable Of T   IEnumerable Of Date   Integer  String    gt    lt  param gt       lt returns gt  The awaiting task   lt  returns gt  Private Async Function AsyncAwaitTask ByVal taskAction As Action  As Task     Me  ActionTask   Task Run taskAction      Await Me ActionTask    Task Run streamEntitiesAction      Try         Me ActionTask  Wait           Me OnStreamTaskEnded If Me ActionTask Is Nothing  TaskStatus RanToCompletion  Me ActionTask Status       Catch ex As AggregateException         Me OnExceptionOccurred ex      Finally         Me TaskCancellationSource Dispose       End Try End Function       lt summary gt  Starts Streaming the events   lt  summary gt       lt exception cref  InvalidOperationException  gt  Thrown when the requested operation is invalid   lt  exception gt       lt param name  bucketKey  gt             The bucket key   lt  param gt       lt param name  timeout  gt               The timeout   lt  param gt       lt param name  streamEntitiesAction  gt  The action to stream the entities  which calls                                          lt see cref  StreamEvents Of T  IEnumerable Of T   IEnumerable Of Date   Integer  String    gt    lt  param gt  Public Overridable Sub StartStreamEvents ByVal bucketKey As String  ByVal timeout As TimeSpan  ByVal streamEntitiesAction As Action      If Me IsTaskActive Then         Throw New InvalidOperationException   Stream task is  Me ActionTask Status        Else         Me  TaskCancellationSource   New Threading CancellationTokenSource         Me TaskCancellationSource Token Register AddressOf Me StreamTaskCanceled          Me TaskCancellationSource CancelAfter timeout            the action class is created withing the Async Await function         Me  AwaitingTask   Me AsyncAwaitTask streamEntitiesAction      End If End Sub

User · Answer

The reason is your result assigned to  the returning Task which represents continuation of your method  and you have a different Task in your method which is running  if you directly assign Task like this you will get your expected results   var task   Task Run      gt                        for  int i   10  i  lt  432543543  i                                     just for a long job                 double d3   Math Sqrt  Math Pow i  5  - Math Pow i  2     Math Sin i   8                             return  Foo Completed                          while  task Status    TaskStatus RanToCompletion                        Console WriteLine  Thread ID   0   Status   1    Thread CurrentThread ManagedThreadId task Status                       Console WriteLine  Result   0    task Result           Console WriteLine  Finished             Console ReadKey true     The output     Consider this for better explanation  You have a Foo method let s say it Task A  and you have a Task in it let s say it Task B  Now the running task  is Task B  your Task A awaiting for Task B result And you assing your result variable to your returning Task which is Task A  because Task B doesn t return a Task  it returns a string  Consider this   If you define your result like this   Task result   Foo 5     You won t get any error But if you define it like this   string result   Foo 5     You will get   Cannot implicitly convert type  System Threading Tasks Task  to  string       But if you add an await keyword   string result   await Foo 5     Again you won t get any error Because it will wait the result  string  and assign it to your result variable So for the last thing consider this  if you add two task into your Foo Method   private static async Task lt string gt  Foo int seconds        await Task Run      gt                        for  int i   0  i  lt  seconds  i                                  Console WriteLine  Thread ID   0   second  1     Thread CurrentThread ManagedThreadId  i                   Task Delay TimeSpan FromSeconds 1   Wait                                  in here don t return anything                 return await Task Run      gt                        for  int i   0  i  lt  seconds  i                                  Console WriteLine  Thread ID   0   second  1     Thread CurrentThread ManagedThreadId  i                   Task Delay TimeSpan FromSeconds 1   Wait                               return  Foo Completed                    And if you run the application  you will get the same results  WaitingForActivation  Because now  your Task A is waiting those two tasks

User · Answer

For my answer  it is worth remembering that the TPL  Task-Parallel-Library   Task class and TaskStatus enumeration were introduced prior to the async-await keywords and the async-await keywords were not the original motivation of the TPL  In the context of methods marked as async  the resulting Task is not a Task representing the execution of the method  but a Task for the continuation of the method  This is only able to make use of a few possible states   Canceled Faulted RanToCompletion WaitingForActivation  I understand that Runningcould appear to have been a better default than WaitingForActivation  however this could be misleading  as the majority of the time  an async method being executed is not actually running  i e  it may be await-ing something else   The other option may have been to add a new value to TaskStatus  however this could have been a breaking change for existing applications and libraries  All of this is very different to when making use of Task Run which is a part of the original TPL  this is able to make use of all the possible values of the TaskStatus enumeration  If you wish to keep track of the status of an async method  take a look at the IProgress T  interface  this will allow you to report the ongoing progress  This blog post  Async in 4 5  Enabling Progress and Cancellation in Async APIs will provide further information on the use of the IProgress T  interface

[c#] Async always WaitingForActivation

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