是否有一种“标准”的方法来指定任务延续应该在创建初始任务的线程上运行?
目前我有下面的代码-它正在工作，但保持跟踪调度程序和创建第二个动作似乎是不必要的开销。
dispatcher = Dispatcher.CurrentDispatcher;
Task task = Task.Factory.StartNew(() =>
{
DoLongRunningWork();
});
Task UITask= task.ContinueWith(() =>
{
dispatcher.Invoke(new Action(() =>
{
this.TextBlock1.Text = "Complete";
}
});
使用TaskScheduler.FromCurrentSynchronizationContext()调用延续:
Task UITask= task.ContinueWith(() =>
{
this.TextBlock1.Text = "Complete";
}, TaskScheduler.FromCurrentSynchronizationContext());
这只适用于当前执行上下文在UI线程上的情况。
如果你有一个返回值需要发送到UI，你可以使用这样的通用版本:
在我的例子中，这是从MVVM视图模型中调用的。
var updateManifest = Task<ShippingManifest>.Run(() =>
{
Thread.Sleep(5000); // prove it's really working!
// GenerateManifest calls service and returns 'ShippingManifest' object
return GenerateManifest();
})
.ContinueWith(manifest =>
{
// MVVM property
this.ShippingManifest = manifest.Result;
// or if you are not using MVVM...
// txtShippingManifest.Text = manifest.Result.ToString();
System.Diagnostics.Debug.WriteLine("UI manifest updated - " + DateTime.Now);
}, TaskScheduler.FromCurrentSynchronizationContext());
我只是想添加这个版本，因为这是一个非常有用的线程，我认为这是一个非常简单的实现。我已经在各种类型的多线程应用程序中多次使用这个:
Task.Factory.StartNew(() =>
{
DoLongRunningWork();
Application.Current.Dispatcher.BeginInvoke(DispatcherPriority.Normal, new Action(() =>
{ txt.Text = "Complete"; }));
});
使用async，你只需要做:
await Task.Run(() => do some stuff);
// continue doing stuff on the same context as before.
// while it is the default it is nice to be explicit about it with:
await Task.Run(() => do some stuff).ConfigureAwait(true);
然而:
await Task.Run(() => do some stuff).ConfigureAwait(false);
// continue doing stuff on the same thread as the task finished on.
通过谷歌来到这里，因为我正在寻找一种很好的方法来在任务内部的ui线程上做事情。运行调用-使用下面的代码，您可以使用await再次返回到UI线程。
我希望这能帮助到一些人。
public static class UI
{
public static DispatcherAwaiter Thread => new DispatcherAwaiter();
}
public struct DispatcherAwaiter : INotifyCompletion
{
public bool IsCompleted => Application.Current.Dispatcher.CheckAccess();
public void OnCompleted(Action continuation) => Application.Current.Dispatcher.Invoke(continuation);
public void GetResult() { }
public DispatcherAwaiter GetAwaiter()
{
return this;
}
}
用法:
... code which is executed on the background thread...
await UI.Thread;
... code which will be run in the application dispatcher (ui thread) ...
