c# - 如何在不阻塞 UI 的情况下等待线程完成

Question

我希望我的程序在下行之后等待

frmProgressBarObj = PullMSI.ExtractByMSIName("products.txt", false);

如上方法是通过StartProcessWithProgress()方法在内部调用线程。我希望该线程在//code logic -2 行被执行之前完成。同时，它不应该停止由 frmProgressBar.UpdateProgress() 完成的 UI 更新。我该怎么做呢？

namespace NS1
{
    public partial class frmMain : Form
    {                
        private void button1_Click(object sender, EventArgs e)
        {
            frmProgressBar frmProgressBarObj = PullMSI.ExtractByMSIName("products.txt", false);
            //code logic - 2
            MessageBox.Show("This is executing immediately. 
                             I want to wait until above thread is complete");
        }
    }

    public partial class frmProgressBar : Form
    {

        public void UpdateProgress(String strTextToDisplayOnProgress)
        {
            progressBar1.BeginInvoke(
                   new Action(() => 
                   { 
                       progressBar1.Value++; 
                       lblFileName.Text = strTextToDisplayOnProgress;
                       if (progressBar1.Value == progressBar1.Maximum)
                       {
                           this.Hide(); 
                        } 
                    }));
        }

        public delegate void DelProgress();

        public void StartProcessWithProgress(DelProgress delMethodCode, int maxCount)
        {
            InitializeProgress(maxCount);
            Thread backgroundThread = new Thread(new ThreadStart(delMethodCode));
            backgroundThread.Start();
        }
    }

    public static class PullMSI
    {
        public static frmProgressBar ExtractByMSIName(String strProductFilePath, bool reNameMSI)
        {
            frmProgressBar frmProgressBar = new frmProgressBar();

            frmProgressBar.StartProcessWithProgress(() =>
            {
                //StreamRader sr declaration and other code

                while (!sr.EndOfStream)
                {
                    //logic here
                    frmProgressBar.UpdateProgress("Copying sr.msiname");
                }
            }, 2);

            return frmProgressBar;
        }
    }
}

Answer 1

我很惊讶你以前没有使用过这些东西，但我真的建议你阅读 C# 中的线程，因为理解复杂性和学习语言从根本上很重要。

以下是您实现目标的三种不同方式:

<强>1。使用重置事件(进一步阅读:https://msdn.microsoft.com/en-us/library/system.threading.manualreseteventslim(v=vs.110).aspx)。如果您的 C# 版本没有 ManualResetEventSlim，请将其替换为 ManualResetEvent 并将 Wait() 更改为 WaitOne()

class LockingWithResetEvents
{
    private readonly ManualResetEvent _resetEvent = new ManualResetEvent(false);

    public void Test()
    {
        MethodUsingResetEvents();
    }

    private void MethodUsingResetEvents()
    {
        ThreadPool.QueueUserWorkItem(_ => DoSomethingLong());
        ThreadPool.QueueUserWorkItem(_ => ShowMessageBox());
    }

    private void DoSomethingLong()
    {
        Console.WriteLine("Doing somthing.");
        Thread.Sleep(1000);
        _resetEvent.Set();
    }

    private void ShowMessageBox()
    {
        _resetEvent.WaitOne();
        Console.WriteLine("Hello world.");
    }
}

2) 使用任务并行库 (TPL)。 进一步阅读:https://msdn.microsoft.com/en-us/library/dd460717(v=vs.110).aspx

class LockingWithTPL
{
    public void Test()
    {
        Task.Factory.StartNew(DoSomethingLong).ContinueWith(result => ShowMessageBox());
    }

    private void DoSomethingLong()
    {
        Console.WriteLine("Doing somthing.");
        Thread.Sleep(1000);
    }

    private void ShowMessageBox()
    {
        Console.WriteLine("Hello world.");
    }
}

3) 使用异步/等待。延伸阅读: https://msdn.microsoft.com/en-us/library/hh191443.aspx

class LockingWithAwait
{
    public void Test()
    {
        DoSomething();
    }

    private async void DoSomething()
    {
        await Task.Run(() => DoSomethingLong());
        ShowMessageBox();
    }

    private async void DoSomethingLong()
    {
        Console.WriteLine("Doing somthing.");
        Thread.Sleep(10000);
    }

    private void ShowMessageBox()
    {
        Console.WriteLine("Hello world.");
    }
}

同样值得一提的是:Mutex(https://msdn.microsoft.com/en-us/library/system.threading.mutex(v=vs.110).aspx)、Semaphore(https://msdn.microsoft.com/en-us/library/system.threading.semaphore(v=vs.110).aspx)、Lock(https://msdn.microsoft.com/en-us/library/c5kehkcz.aspx)、SemaphoreSlim(https://msdn.microsoft.com/en-us/library/system.threading.semaphoreslim(v=vs.110).aspx)、Monitor(https://msdn.microsoft.com/en-us/library/system.threading.monitor(v=vs.110).aspx)和 Interlocked(https://msdn.microsoft.com/en-us/library/system.threading.interlocked(v=vs.110).aspx)。