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 程式師世界 >> 編程語言 >> .NET網頁編程 >> C# >> C#入門知識 >> 詳細解析C#多線程同步事情及等候句柄

詳細解析C#多線程同步事情及等候句柄

編輯:C#入門知識

詳細解析C#多線程同步事情及等候句柄。本站提示廣大學習愛好者:(詳細解析C#多線程同步事情及等候句柄)文章只能為提供參考,不一定能成為您想要的結果。以下是詳細解析C#多線程同步事情及等候句柄正文


最近搗鼓了一下多線程的同步問題,發現其實C#關於多線程同步事情處置還是很靈敏,這裡次要寫一下,自己測試的一些代碼,觸及到了AutoResetEvent 和 ManualResetEvent,當然還有也扼要提了一下System.Threading.WaitHandle.WaitOne 、System.Threading.WaitHandle.WaitAny和System.Threading.WaitHandle.WaitAll ,上面我們一最初學者的角度來看,多線程之間的同步。

假定有這樣的一個場景,主線程開了一個子線程,讓子線程等著,等主線程完成了某件事情時再告訴子線程去往下執行,這裡關鍵就在於這個怎讓子線程等著,主線程怎告訴子線程,普通狀況下我們不難想到用一個公共變量,於是我們就有了上面的代碼:

using System; 
using System.Collections.Generic; 
using System.Text; 
using System.Threading; 
 
namespace AutoResetEventTest 
{ 
  class Class1 
  { 
    static bool flag = true; 
 
    static void DoWork() 
    { 
      Console.WriteLine("  worker thread started, now waiting on event..."); 
      while (flag) 
      { 
 
      } 
      Console.WriteLine("  worker thread reactivated, now exiting..."); 
    } 
 
    static void Main() 
    { 
      Console.WriteLine("main thread starting worker thread..."); 
      Thread t = new Thread(DoWork); 
      t.Start(); 
 
      Console.WriteLine("main thrad sleeping for 1 second..."); 
      Thread.Sleep(1000); 
 
      Console.WriteLine("main thread signaling worker thread..."); 
      flag = false; 
    } 
  } 
} 

雖然目的到達了,但是看著這代碼就糾結,上面該是我們的配角上場了,AutoResetEvent 和 ManualResetEvent,關於這兩者我們暫且以為是差不多了,稍後我會引見他們的不同,這裡以AutoResetEvent為例,其實很多官方的說法太過於籠統,這裡淺顯地講,可以以為AutoResetEvent就是一個公共的變量(雖然它是一個事情),創立的時分可以設置為false,然後在要等候的線程運用它的WaitOne辦法,那麼線程就不斷會處於等候形態,只要這個AutoResetEvent被別的線程運用了Set辦法,也就是要發告訴的線程運用了它的Set辦法,那麼等候的線程就會往下執行了,Set就是發信號,WaitOne是等候信號,只要發了信號,等候的才會執行。假如不發的話,WaitOne前面的順序就永遠不會執行。好上面看用AutoResetEvent改造下面的順序:

using System; 
using System.Collections.Generic; 
using System.Text; 
using System.Threading; 
 
namespace AutoResetEventTest 
{ 
  class Class2 
  { 
    static AutoResetEvent mEvent=new AutoResetEvent(false); 
    //static ManualResetEvent mEvent = new ManualResetEvent(false); 
 
    static void DoWork() 
    { 
      Console.WriteLine("  worker thread started, now waiting on event..."); 
      mEvent.WaitOne(); 
      Console.WriteLine("  worker thread reactivated, now exiting..."); 
    } 
 
    static void Main() 
    { 
      Console.WriteLine("main thread starting worker thread..."); 
      Thread t = new Thread(DoWork); 
      t.Start(); 
 
      Console.WriteLine("main thrad sleeping for 1 second..."); 
      Thread.Sleep(1000); 
 
      Console.WriteLine("main thread signaling worker thread..."); 
      mEvent.Set(); 
    } 
  } 
} 

這時代碼是不是清新多了,這裡其實你還會看到,把下面的AutoResetEvent換成ManualResetEvent也是沒有問題的,那麼它兩之間的區別是什麼呢?團體以為它們最大的區別在於,無論何時,只需 AutoResetEvent 激活線程,它的形態將自動從終止變為非終止。相反,ManualResetEvent 允許它的終止形態激活恣意多個線程,只要當它的 Reset 辦法被調用時才復原到非終止形態。開上面的代碼:

using System; 
using System.Collections.Generic; 
using System.Text; 
using System.Threading; 
 
namespace AutoResetEventTest 
{ 
  class Class3 
  { 
    static AutoResetEvent mEvent = new AutoResetEvent(false); 
    //static ManualResetEvent mEvent = new ManualResetEvent(false); 
 
    static void DoWork() 
    { 
      Console.WriteLine("  worker thread started, now waiting on event..."); 
      for (int i = 0; i < 3; i++) 
      { 
        mEvent.WaitOne(); 
        //mEvent.Reset(); 
        Console.WriteLine("  worker thread reactivated, now exiting..."); 
      } 
    } 
 
    static void Main() 
    { 
      Console.WriteLine("main thread starting worker thread..."); 
      Thread t = new Thread(DoWork); 
      t.Start(); 
 
      for (int i = 0; i < 3; i++) 
      { 
        Thread.Sleep(1000); 
        Console.WriteLine("main thread signaling worker thread..."); 
        mEvent.Set(); 
      } 
    } 
  } 
} 

假如你想僅僅把AutoResetEvent換成ManualResetEvent的話,你發現輸入就會亂套了,為什麼呢?

假設有autoevent.WaitOne()和manualevent.WaitOne(),當線程失掉信號後都得以持續執行。差異就在調用後,autoevent.WaitOne()每次只允許一個線程進入,當某個線程失掉信號(也就是有其他線程調用了autoevent.Set()辦法後)後,autoevent會自動又將信號置為不發送形態,則其他調用WaitOne的線程只要持續等候,也就是說,autoevent一次只喚醒一個線程。而manualevent則可以喚醒多個線程,當某個線程調用了set辦法後,其他調用waitone的線程取得信號得以持續執行,而manualevent不會自動將信號置為不發送,也就是說,除非手工調用了manualevent.Reset()辦法,否則manualevent將不斷堅持有信號形態,manualevent也就可以同時喚醒多個線程持續執行。

在下面代碼中,假如將AutoResetEvent換成ManualResetEvent的話,只需要在waitone前面做下reset,就會到達異樣的效果。

之後我們再來個復雜的例子:

using System; 
using System.Collections.Generic; 
using System.Text; 
using System.Threading; 
 
namespace AutoResetEventTest 
{ 
  class Class4 
  { 
    public static AutoResetEvent mEvent = new AutoResetEvent(false); 
 
    public static void trmain() 
    { 
      Thread tr = Thread.CurrentThread; 
      Console.WriteLine("thread: waiting for an event"); 
      mEvent.WaitOne(); 
      Console.WriteLine("thread: got an event"); 
      for (int x = 0; x < 10; x++) 
      { 
        Thread.Sleep(1000); 
        Console.WriteLine(tr.Name + ": " + x); 
      } 
    } 
    static void Main(string[] args) 
    { 
      Thread thrd1 = new Thread(new ThreadStart(trmain)); 
      thrd1.Name = "thread1"; 
      thrd1.Start(); 
      for (int x = 0; x < 10; x++) 
      { 
        Thread.Sleep(900); 
        Console.WriteLine("Main:" + x); 
        if (5 == x) mEvent.Set(); 
      } 
      while (thrd1.IsAlive) 
      { 
        Thread.Sleep(1000); 
        Console.WriteLine("Main: waiting for thread to stop"); 
      } 
    } 
  } 
} 

是不是更有覺得了?之後咱來看看另外幾個東東:

System.Threading.WaitHandle.WaitOne 使線程不斷等候,直到單個事情變為終止形態;

System.Threading.WaitHandle.WaitAny 阻止線程,直到一個或多個指示的事情變為終止形態;

System.Threading.WaitHandle.WaitAll 阻止線程,直到一切指示的事情都變為終止形態。

然後再來個例子,以WaitAll運用為例:

using System; 
using System.Collections.Generic; 
using System.Text; 
using System.Threading; 
 
namespace AutoResetEventTest 
{ 
  class other 
  { 
    static void Main(string[] args) 
    { 
      Random randomGenerator = new Random(); 
      AutoResetEvent[] resets=new AutoResetEvent[5]; 
 
      for (int i = 0; i < 5; i++) 
      { 
        resets[i] = new AutoResetEvent(false); 
        int wTime = randomGenerator.Next(10)+1; 
 
        worker w = new worker(wTime, resets[i]); 
 
        Thread thrd1 = new Thread(new ThreadStart(w.work)); 
        thrd1.Start();  
      } 
      WaitHandle.WaitAll(resets); 
      Console.WriteLine("ALL worker done - main exiting."); 
    } 
 
  } 
 
  public class worker 
  { 
    public string name; 
    public int wTime; 
    public AutoResetEvent mEvent; 
 
    public worker(int w, AutoResetEvent m) 
    { 
      name = w.ToString(); 
      wTime = w * 1000; 
      mEvent = m; 
    } 
 
    public void work() 
    { 
      Console.WriteLine(name + " worker thread waiting for " + wTime + "...."); 
      Thread.Sleep(wTime); 
      Console.WriteLine(name + " worker thread back..."); 
      mEvent.Set(); 
    } 
  } 
} 

復雜來說就是,開了5個線程,每個線程隨機休眠若干秒,都完成後告訴主線程加入,這裡就開了一個AutoResetEvent數組,主線程就WaitHandle.WaitAll(resets) ,子線程休眠完後就Set1個AutoResetEvent,最後都Set完後,主線程就會往下執行。最後最後再來個買書付款取貨的例子,加深了解:

using System; 
using System.Collections.Generic; 
using System.Text; 
using System.Threading; 
 
namespace AutoResetEventTest 
{ 
  class Program 
  { 
    const int numIterations = 10; 
    static AutoResetEvent myResetEvent = new AutoResetEvent(false); 
    static AutoResetEvent ChangeEvent = new AutoResetEvent(false); 
    //static ManualResetEvent myResetEvent = new ManualResetEvent(false); 
    //static ManualResetEvent ChangeEvent = new ManualResetEvent(false); 
    static int number; //這是關鍵資源 
 
    static void Main() 
    { 
      Thread payMoneyThread = new Thread(new ThreadStart(PayMoneyProc)); 
      payMoneyThread.Name = "付錢線程"; 
      Thread getBookThread = new Thread(new ThreadStart(GetBookProc)); 
      getBookThread.Name = "取書線程"; 
      payMoneyThread.Start(); 
      getBookThread.Start(); 
 
      for (int i = 1; i <= numIterations; i++) 
      { 
        Console.WriteLine("買書線程:數量{0}", i); 
        number = i; 
        //Signal that a value has been written. 
        myResetEvent.Set(); 
        //ChangeEvent.Set(); 
        Thread.Sleep(10); 
      } 
      payMoneyThread.Abort(); 
      getBookThread.Abort(); 
    } 
 
    static void PayMoneyProc() 
    { 
      while (true) 
      { 
        myResetEvent.WaitOne(); 
        //myResetEvent.Reset(); 
        Console.WriteLine("{0}:數量{1}", Thread.CurrentThread.Name, number); 
        ChangeEvent.Set(); 
      } 
    } 
    static void GetBookProc() 
    { 
      while (true) 
      { 
        ChangeEvent.WaitOne(); 
        //ChangeEvent.Reset();         
        Console.WriteLine("{0}:數量{1}", Thread.CurrentThread.Name, number); 
        Console.WriteLine("------------------------------------------"); 
        //Thread.Sleep(0); 
      } 
    } 
  } 
} 

以上就是本文的全部內容,希望對大家的學習有所協助,也希望大家多多支持。

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