Wait some seconds without blocking UI execution

Question

I would like to wait some seconds between two instruction  but WITHOUT blocking the execution   For example  Thread Sleep 2000  it is not good  because it blocks execution   The idea is that I call a method and then I wait X seconds  20 for example  listening for an event coming  At the end of the 20 seconds I should do some operation depending on what happened in the 20 seconds

User · Answer

If possible  the preferred approach should be using an asynchronous way or a second thread  If this isn t possible or wanted  using any implementation of DoEvents   is a bad idea  since it may cause problems Possible problems with DoEvents  This is mostly about DoEvents with Winforms but the possible pitfalls in WPF are the same  Then putting a frame on the Dispatcher with the wanted sleep time can be used  using System  using System Threading  using System Windows Threading   public static void NonBlockingSleep int timeInMilliseconds        DispatcherFrame df   new DispatcherFrame         new Thread  ThreadStart       gt                Thread Sleep TimeSpan FromMilliseconds timeInMilliseconds            df Continue   false           Start         Dispatcher PushFrame df

User · Answer

Look into System Threading Timer class   I think this is what you re looking for  The code example on MSDN seems to show this class doing very similar to what you re trying to do  check status after certain time   The mentioned code example from the MSDN link  using System  using System Threading   class TimerExample       static void Main                    Create an AutoResetEvent to signal the timeout threshold in the            timer callback has been reached          var autoEvent   new AutoResetEvent false                    var statusChecker   new StatusChecker 10               Create a timer that invokes CheckStatus after one second              and every 1 4 second thereafter          Console WriteLine  quot  0 h mm ss fff  Creating timer  n quot                            DateTime Now           var stateTimer   new Timer statusChecker CheckStatus                                   autoEvent  1000  250               When autoEvent signals  change the period to every half second          autoEvent WaitOne            stateTimer Change 0  500           Console WriteLine  quot  nChanging period to  5 seconds  n quot                When autoEvent signals the second time  dispose of the timer          autoEvent WaitOne            stateTimer Dispose            Console WriteLine  quot  nDestroying timer  quot             class StatusChecker       private int invokeCount      private int  maxCount       public StatusChecker int count                invokeCount    0          maxCount   count                This method is called by the timer delegate      public void CheckStatus Object stateInfo                AutoResetEvent autoEvent    AutoResetEvent stateInfo          Console WriteLine  quot  0  Checking status  1 2   quot                DateTime Now ToString  quot h mm ss fff quot                    invokeCount  ToString              if invokeCount    maxCount                           Reset the counter and signal the waiting thread              invokeCount   0              autoEvent Set                         The example displays output like the following           11 59 54 202 Creating timer                     11 59 55 217 Checking status  1           11 59 55 466 Checking status  2           11 59 55 716 Checking status  3           11 59 55 968 Checking status  4           11 59 56 218 Checking status  5           11 59 56 470 Checking status  6           11 59 56 722 Checking status  7           11 59 56 972 Checking status  8           11 59 57 223 Checking status  9           11 59 57 473 Checking status 10                     Changing period to  5 seconds                     11 59 57 474 Checking status  1           11 59 57 976 Checking status  2           11 59 58 476 Checking status  3           11 59 58 977 Checking status  4           11 59 59 477 Checking status  5           11 59 59 977 Checking status  6           12 00 00 478 Checking status  7           12 00 00 980 Checking status  8           12 00 01 481 Checking status  9           12 00 01 981 Checking status 10                     Destroying timer

User · Answer

This is a good case for using another thread      Call some method this Method     Task Factory StartNew      gt        Thread Sleep 20000           Do things here         NOTE  You may need to invoke this to your main thread depending on what you re doing       The above code expects  NET 4 0 or above  otherwise try   ThreadPool QueueUserWorkItem new WaitCallback delegate       Thread Sleep 20000           Do things here

User · Answer

I use   private void WaitNSeconds int segundos        if  segundos  lt  1  return      DateTime  desired   DateTime Now AddSeconds segundos       while  DateTime Now  lt   desired             System Windows Forms Application DoEvents

User · Answer

In my case I needed to do this because I had passed a method to the thread I was waiting for and that caused the lock becuase the metod was run on the GUI thread and the thread code called that method sometimes  Task lt string gt  myTask   Task Run      gt           Your code or method call     return  quot Maybe you want to return other datatype  then just change it  quot          Some other code maybe    while  true        myTask Wait 10       Application DoEvents        if  myTask IsCompleted  break

User · Answer

Omar s solution is decent  if you cannot upgrade your environment to  NET 4 5 in order to gain access to the async and await APIs   That said  there here is one important change that should be made in order to avoid poor performance   A slight delay should be added between calls to Application DoEvents   in order to prevent excessive CPU usage   By adding     Thread Sleep 1     before the call to Application DoEvents    you can add such a delay  1 millisecond  and prevent the application from using all of the cpu cycles available to it   private void WaitNSeconds int seconds        if  seconds  lt  1  return      DateTime  desired   DateTime Now AddSeconds seconds       while  DateTime Now  lt   desired             Thread Sleep 1            System Windows Forms Application DoEvents               See https   blog codinghorror com is-doevents-evil  for a more detailed discussion on the potential pitfalls of using Application DoEvents

User · Answer

I think what you are after is Task Delay  This doesn t block the thread like Sleep does and it means you can do this using a single thread using the async programming model   async Task PutTaskDelay         await Task Delay 5000       private async void btnTaskDelay Click object sender  EventArgs e        await PutTaskDelay        MessageBox Show  I am back

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If you do not want to block things and also not want to use multi threading  here is the solution for you  https   msdn microsoft com en-us library system timers timer v vs 110  aspx  The UI Thread is not blocked and the timer waits for 2 seconds before doing something   Here is the code coming from the link above              Create a timer with a two second interval      aTimer   new System Timers Timer 2000          Hook up the Elapsed event for the timer       aTimer Elapsed    OnTimedEvent      aTimer Enabled   true       Console WriteLine  Press the Enter key to exit the program            Console ReadLine        Console WriteLine  Terminating the application

User · Answer

i really disadvise you against using Thread Sleep 2000   because of a several reasons  a few are described here   but most of all because its not useful when it comes to debugging testing   I recommend to use a C  Timer instead of Thread Sleep    Timers let you perform methods frequently  if necessary  AND are much easiert to use in testing  There s a very nice example of how to use a timer right behind the hyperlink - just put your logic  what happens after 2 seconds  right into the Timer Elapsed    new ElapsedEventHandler OnTimedEvent   method

User · Answer

hi this is my suggestion          var t   Task Run async      gt  await Task Delay TimeSpan FromSeconds Consts FiveHundred   ConfigureAwait false                      just to wait task is done                 t Wait     keep in mind put the  quot wait quot  otherwise the Delay run without affect application

[c#] Wait some seconds without blocking UI execution

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