[英]Reporting Progress from Tasks
在使用Task的WhenAll()或WaitAll()方法時,是否有辦法了解單個任務的狀態。
當我對每個完成的任務使用await Task.WhenAll(tasks.ToArray())時,我想知道該任務已完成。
可能有一種更好的方法,但這是一個原始類,該類接收未啟動的任務數組,並在每次某些任務完成執行時觸發事件:
public class TaskBatchRunner
{
private Task[] _tasks;
public event EventHandler<Task> TaskCompleted;
public TaskBatchRunner(Task[] tasks)
{
_tasks = tasks.Select(t =>
new Task(() =>
{
t.ContinueWith(OnTaskCompleted);
t.Start();
})).ToArray();
}
public void Run()
{
foreach (var t in _tasks) t.Start();
Task.WaitAll(_tasks);
}
private void OnTaskCompleted(Task completedTask)
{
TaskCompleted?.Invoke(this, completedTask);
}
}
用法:
var taskRunner = new TaskBatchRunner(tasks.ToArray());
taskRunner.TaskCompleted += MyTaskCompleted;
taskRunner.Run();
...
private void MyTaskCompleted(object sender, Task e)
{
System.Diagnostics.Debug.WriteLine($"task {e.Id} completed!");
}
要報告async
或並發進程的進度,請使用IProgress<T>
抽象。 使用Progress<T>
您可以在后台進行工作時輕松捕獲當前上下文並在ui上下文上運行進度更新/完成表達式:
public class WorkItem {
public async Task DoWork(IProgress<bool> completionNotification) {
await Task.Delay(TimeSpan.FromSeconds(2));
//Work Done
completionNotification.Report(true);
}
//Get, Set, Fire Property change etc
public bool Completed {
get; set;
}
}
public class ViewModel {
public async void ButtonClickHandler(object sender, EventArgs e) {
var workitemTasks = WorkItems.Select(workItem =>
workItem.DoWork(new Progress<bool>(done => workItem.Completed = done)))
.ToList();
await Task.WhenAll(workitemTasks);
}
//Get, Set, Fire Property change etc
public IEnumerable<WorkItem> WorkItems {
get; set;
}
}
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