没有 ui 冻结的 Task.Factory.StartNew 延迟

Question

当我在UpdateGuItemsAsync 中使用Thread.Sleep 时，程序冻结10 秒，因为线程被阻塞。如果我在“UpdateGuItemsAsync”中使用Task.Delay，代码会立即执行而不会暂停。我希望在不冻结 UI 的情况下在列表更新之前得到延迟。如何在 .net 3.5 中做到这一点？

TaskScheduler uiScheduler = TaskScheduler.FromCurrentSynchronizationContext();
Task.Factory.StartNew(UpdateGuItemsAsync, CancellationToken.None, TaskCreationOptions.None, uiScheduler);


    public void UpdateGuItemsAsync()
    {
        System.Threading.Thread.Sleep(10000);
        for (int i = 0; i < 100; i++)
        {
            Gu45Document gu45Document = new Gu45Document();
            gu45Document.Form = "EU-45";
            Gu45Documents.Add(gu45Document);
        }
    }

Answer 1

编辑

抱歉，我错过了关于 .Net 3.5 导致 Task.Delay 谈话的要点。下面在 .net 3.5 中找到一个示例，该示例在 10 秒后更新表单中的进度条。按下该表单中的按钮时：

using System;
using System.Threading;
using System.Windows.Forms;

  public partial class Form1 : Form
  {
    public Form1()
    {
      InitializeComponent();
    }

    delegate void UpdateGuItemsAsyncDelegate();
    void UpdateGuItemsAsync()
    {
      for (int i = 0; i < 100; i++)
      {
        progressBar1.PerformStep();
      }
    }

    private void button1_Click(object sender, EventArgs e)
    {
      ThreadPool.QueueUserWorkItem(state =>
      {
        Thread.Sleep(10000);

        if (progressBar1.InvokeRequired)
        {
          UpdateGuItemsAsyncDelegate del = new UpdateGuItemsAsyncDelegate(UpdateGuItemsAsync);
          this.Invoke(del);
        }
        else
        {
          UpdateGuItemsAsync();
        }

      });
    }
  }

在 WPF/XAML 中，如果窗口中有进度条和按钮，您几乎可以执行相同的操作：

  <StackPanel>
    <ProgressBar Name="ProgBar" Minimum="0" Maximum="100" Height="20" />
    <Button Name="UpdateCmd" Click="UpdateCmd_Click" Content="Update" />
  </StackPanel>

在代码中：

private void UpdateCmd_Click(object sender, RoutedEventArgs e)
{
  ThreadPool.QueueUserWorkItem(state =>
  {
    Thread.Sleep(10000);

    for (int i = 0; i < 100; i++)
    {
      Dispatcher.Invoke(new Action(() =>
      {
        ProgBar.Value++;
      }));

      Thread.Sleep(50);
    }
  });
}

Answer 2

在您的情况下，我会使用System.Windows.Threading.DispatcherTimer 并让它在 10 秒后运行一个事件。这适用于 WPF 和 WinForms，但是如果您的项目是 winforms，则需要在项目引用中添加对 WindowsBase 的引用。

private void UpdateGuItemsAsync()
{
    //This line must be called on the UI thread
    var timer = new DispatcherTimer();
    timer.Interval = TimeSpan.FromSeconds(10);
    timer.Tick += OnUpdateGuiItemsTimerTick;
    timer.Start();
}

private void OnUpdateGuiItemsTimerTick(object sender, EventArgs e)
{
    //Stop the timer.
    var timer = sender as DispatcherTimer;
    timer.Stop();

    //Run the code you where waiting for.
    for (int i = 0; i < 100; i++)
    {
        Gu45Document gu45Document = new Gu45Document();
        gu45Document.Form = "EU-45";
        Gu45Documents.Add(gu45Document);
    }
}

以下是您在 .NET 3.5 中运行并运行的独立程序，以查看它是否有效。您需要做的就是创建一个新的 Windows 窗体项目，添加对 WindowsBase 的引用并使用以下代码

using System;
using System.Windows.Forms;
using System.Windows.Threading;

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
            this.Load += Form1_Load;
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            UpdateGuiItems();
        }

        private void UpdateGuiItems()
        {
            var timer = new DispatcherTimer();
            timer.Interval = TimeSpan.FromSeconds(5);
            timer.Tick += OnUpdateGuiItemsTimerTick;
            timer.Start();
        }

        private void OnUpdateGuiItemsTimerTick(object sender, EventArgs e)
        {
            var timer = sender as DispatcherTimer;
            timer.Stop();

            MessageBox.Show("Am I on the UI thread: " + !this.InvokeRequired);
        }
    }
}

Answer 3

这应该可以完成工作

TaskScheduler uiScheduler = TaskScheduler.FromCurrentSynchronizationContext();
Task.Factory.StartNew( () => Thread.Sleep( 10000 ) )
    .ContinueWith(
        t => UpdateGuItemsAsync(),
        CancellationToken.None,
        TaskContinuationOptions.None,
        uiScheduler );

public void UpdateGuItemsAsync()
{
    // System.Threading.Thread.Sleep(10000);
    for (int i = 0; i < 100; i++)
    {
        Gu45Document gu45Document = new Gu45Document();
        gu45Document.Form = "EU-45";
        Gu45Documents.Add(gu45Document);
    }
}

我正在使用 NuGet 包Task Parallel Library for .NET 3.5。

Answer 4

您可以使用System.Windows.Forms.Timer，它在等待 10 秒时不会阻塞 UI：

 public void UpdateGuItemsAsync()
 {
    System.Windows.Forms.Timer timer = new System.Windows.Forms.Timer();
    timer.Interval = 10000;
    timer.Tick += (sender, args) => 
    {
        timer.Stop();
        for (int i = 0; i < 100; i++)
        {
            Gu45Document gu45Document = new Gu45Document();
            gu45Document.Form = "EU-45";
            Gu45Documents.Add(gu45Document);
        }
    };
    timer.Start();  
 }