Async and Await Blocking Ui[Answered] RSS

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  Chan Leo

  Member

  15 Points

  23 Posts

  Async and Await Blocking Ui

  Oct 29, 2019 11:18 AM|Chan Leo|LINK

  I am new to ASP.Net Mvc , i have gone through some async and await video and articles,so i use it in my action like

  public IActionResult Index()
  {
      var jsonTask  = await GetJsonAsync(new Uri("https://jsonplaceholder.typicode.com/comments"));
      LogEvent("Index","Async operation 1 started");
      var jsonTask2 = await GetJsonAsync(new Uri("https://jsonplaceholder.typicode.com/comments"));
      LogEvent("Index","Operation 2 started");
  
      ViewBag.Result1= jsonTask;
      ViewBag.Resulr2 = jsonTask2;
  
     return View();
  
  }

  Issue is when i debug the application it execute in sequential order and jsonTask1 then LogEvent(...) and so on, why my LogEvent is not fire when doing async job of JsonTask1 and why control not goes to View if it is async processing of Json Tasks.
  
  

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  PatriceSc

  All-Star

  48720 Points

  18184 Posts

  Re: Async and Await Blocking Ui

  Oct 29, 2019 11:54 AM|PatriceSc|LINK

  Hi,

  This is mainly for web forms but https://docs.microsoft.com/en-us/aspnet/web-forms/overview/performance-and-caching/using-asynchronous-methods-in-aspnet-45#Parallel applies as well.

  The xxxAsync method starts the operation and await allows to wait for this operation to be completed. This is the usual pattern when you have a single async operation or needs to make them one after the other.

  The code sample shows how to call just the xxxAsync methods to start them all and then you'll await on all of them so that  the next line happens when all are ended...

• • Reply
  Khuram.Shahz...

  Contributor

  2096 Points

  1040 Posts

  Re: Async and Await Blocking Ui

  Oct 30, 2019 03:32 AM|Khuram.Shahzad|LINK

  When you use await key word with a function then it start waiting for the result and not going further, to do some operations in parallel you need to initiate the functions and then wait for their completion after sync or other method that need to be executed in parallel.

  like

      /// <returns></returns>
          public async Task<IActionResult> Index()
          {
              //Fire
              var t1 =  GetAsync(); //starting        
              var t2 =  GetAsync(); //starting 
              var t3 =  GetAsync(); //starting
              
              AnySyncMethod();      //processing
              Debug.WriteLine("Other operation");   //done
              Debug.WriteLine("Good going");        //done
              
  
              //May be at this time t1 or t2 or t3 already done beause of parallel execution 
              var r1 = await t1;   //waiting for result
              var r2 = await t2;   //waiting for result
              var r3 = await t3;   //waiting for result
  
                  
              return View();
          }

  "Mark as Answer" if that helps you.