如何等待線程不會阻塞UI

Question

完成我希望我的程序等待下面一行

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

如上述方法在內部調用通過StartProcessWithProgress線程（）方法後。我希望線程在//代碼邏輯-2行被執行之前完成。同時，它不應該停止由frmProgressBar.UpdateProgress（）完成UI更新。我該怎麼做呢？

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

我很驚訝你之前沒有使用過任何這些工具，但是我真的會推薦閱讀關於C＃中的線程，因爲了解錯綜複雜和學習語言是非常重要的。

下面是三種不同的方法，你可以達到你想要的東西：

1.使用復位事件（延伸閱讀：https://msdn.microsoft.com/en-us/library/system.threading.manualreseteventslim(v=vs.110).aspx）。如果你的C＃版本不具備ManualResetEventSlim，與ManualResetEvent替換和更改Wait()與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）使用任務並行庫（TPL）。進一步閱讀：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）使用異步/等待。延伸閱讀：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."); 
    } 
} 

還不錯知道：互斥（https://msdn.microsoft.com/en-us/library/system.threading.mutex(v=vs.110).aspx），信號量（https://msdn.microsoft.com/en-us/library/system.threading.semaphore(v=vs.110).aspx），鎖（https://msdn.microsoft.com/en-us/library/c5kehkcz.aspx），SemaphoreSlim（https://msdn.microsoft.com/en-us/library/system.threading.semaphoreslim(v=vs.110).aspx），監視器（https://msdn.microsoft.com/en-us/library/system.threading.monitor(v=vs.110).aspx）和互鎖（https://msdn.microsoft.com/en-us/library/system.threading.interlocked(v=vs.110).aspx）。

Answer 2

如果你使用.NET 4.0（與VS2012）或以上，你可以做到這一點很容易與Task Parallel Library和async-await：

private async void button1_Click(object sender, EventArgs e) 
{ 
    frmProgressBar frmProgressBarObj = await Task.Run(() => 
         PullMSI.ExtractByMSIName("products.txt", false)); 

    MessageBox.Show(string.Format("Returned {0}", frmProgressBarObj.ToString()); 
} 

對於.NET 4，你需要添加Microsoft.Bcl.Async。