Skip to main content

Task - run on UI thread (update UI)

Working with Tasks is pretty easy. You can do very easy things that would be pretty complicated to do using threads. In today post I want to talk a little bit about UI threads and tasks.
If you are working on a Windows Store App, Windows Phone or WPF application then you will have the following case:
From a task I want to be able to update a UI component (a label for example).
By default this is not possible, if you are trying to run the task from the UI thread then you don’t resolve the problem. The task will still run on the UI thread and if you have a long task then you will block the UI.
The solution is to run only the lines of code that update the UI components on a task that runs on UI. If the code that updates the UI is at the end of the task then you can have something like this:
var blueTask = Task<string>.Run(() =>
  {
    ...
    return value;
  })
  .ContinueWith(value =>
  {
    ...
    this.MyLabel.Text = value;
  }, TaskScheduler.FromCurrentSynchronizationContext());
If the code has to display a dialog box and you need a response then you can create a task inside your task that runs on the UI task:
var uiScheduler = TaskScheduler.FromCurrentSynchronizationContext;
var blueTask = Task<string>.Run(() =>
  {
    ...
     await Task.Factory.StartNew(
              () => this.MyLabel.Text = value,
              CancellationToken.None, TaskCreationOptions.None, uiScheduler);

    return value;
  });
Enjoy!

Comments

Popular posts from this blog

Windows Docker Containers can make WIN32 API calls, use COM and ASP.NET WebForms

After the last post , I received two interesting questions related to Docker and Windows. People were interested if we do Win32 API calls from a Docker container and if there is support for COM. WIN32 Support To test calls to WIN32 API, let’s try to populate SYSTEM_INFO class. [StructLayout(LayoutKind.Sequential)] public struct SYSTEM_INFO { public uint dwOemId; public uint dwPageSize; public uint lpMinimumApplicationAddress; public uint lpMaximumApplicationAddress; public uint dwActiveProcessorMask; public uint dwNumberOfProcessors; public uint dwProcessorType; public uint dwAllocationGranularity; public uint dwProcessorLevel; public uint dwProcessorRevision; } ... [DllImport("kernel32")] static extern void GetSystemInfo(ref SYSTEM_INFO pSI); ... SYSTEM_INFO pSI = new SYSTEM_INFO(

ADO.NET provider with invariant name 'System.Data.SqlClient' could not be loaded

Today blog post will be started with the following error when running DB tests on the CI machine: threw exception: System.InvalidOperationException: The Entity Framework provider type 'System.Data.Entity.SqlServer.SqlProviderServices, EntityFramework.SqlServer' registered in the application config file for the ADO.NET provider with invariant name 'System.Data.SqlClient' could not be loaded. Make sure that the assembly-qualified name is used and that the assembly is available to the running application. See http://go.microsoft.com/fwlink/?LinkId=260882 for more information. at System.Data.Entity.Infrastructure.DependencyResolution.ProviderServicesFactory.GetInstance(String providerTypeName, String providerInvariantName) This error happened only on the Continuous Integration machine. On the devs machines, everything has fine. The classic problem – on my machine it’s working. The CI has the following configuration: TeamCity .NET 4.51 EF 6.0.2 VS2013 It see

Navigating Cloud Strategy after Azure Central US Region Outage

 Looking back, July 19, 2024, was challenging for customers using Microsoft Azure or Windows machines. Two major outages affected customers using CrowdStrike Falcon or Microsoft Azure computation resources in the Central US. These two outages affected many people and put many businesses on pause for a few hours or even days. The overlap of these two issues was a nightmare for travellers. In addition to blue screens in the airport terminals, they could not get additional information from the airport website, airline personnel, or the support line because they were affected by the outage in the Central US region or the CrowdStrike outage.   But what happened in reality? A faulty CrowdStrike update affected Windows computers globally, from airports and healthcare to small businesses, affecting over 8.5m computers. Even if the Falson Sensor software defect was identified and a fix deployed shortly after, the recovery took longer. In parallel with CrowdStrike, Microsoft provided a too