C# Eventi tra thread eseguiti nella loro stessa discussione (Come fare)?

Question

Mi piacerebbe avere due thread. Chiamiamoli così:

• Discussione Un
• Discussione B

Thread A genera un evento e filo B ascoltare a questo evento. Quando viene eseguito l'evento Listener evento di Thread B, viene eseguito con l'ID thread di Thread A, quindi suppongo che venga eseguito all'interno del thread A.

Quello che mi piacerebbe fare è essere in grado di sparare all'evento a Thread B dicendo qualcosa del tipo: "hey, un dato è pronto per te, ora puoi occupartene". Questo evento deve essere eseguito nel proprio Thread perché utilizza cose a cui solo lui può accedere (come i controlli dell'interfaccia utente).

Come posso farlo?

Grazie per il vostro aiuto.

Answer 1

È necessario eseguire il marshalling delle informazioni nel thread dell'interfaccia utente.

In genere, è necessario gestirlo nel gestore eventi. Ad esempio, supponiamo che il thread A sia il thread dell'interfaccia utente: quando si abbona a un evento su un oggetto in Thread B, il gestore di eventi verrà eseguito all'interno del thread B. Tuttavia, può quindi eseguire il marshalling nel thread dell'interfaccia utente:

// In Thread A (UI) class... 
private void myThreadBObject_EventHandler(object sender, EventArgs e) 
{ 
    this.button1.BeginInvoke(new Action(
     () => 
      { 
       // Put your "work" here, and it will happen on the UI thread... 
      })); 
} 

Answer 2

il modo più semplice è probabilmente quello di abbonarsi utilizzando un gestore di eventi che ha appena maresciallo la chiamata "reale" del gestore sul filo B. per esempio, il gestore potrebbe chiamare Control.BeginInvoke fare un certo lavoro sul filetto B:

MethodInvoker realAction = UpdateTextBox; 
foo.SomeEvent += (sender, args) => textBox.BeginInvoke(realAction); 

... 

private void UpdateTextBox() 
{ 
    // Do your real work here 
} 

Answer 3

Se si utilizza Windows Form o WPF e non si dispone di un riferimento di controllo a portata di mano dai gestori di eventi, è anche possibile acquisire il riferimento e di System.Threading.SynchronizationContext.Current in qualcosa in esecuzione sul thread dell'interfaccia utente ed esporre tale riferimento ai gestori di eventi.

Poi, quando è necessario avere qualcosa di eseguire sul thread dell'interfaccia utente, richiamare Post() o Send() sul catturato SynchronizationContext di riferimento dal vostro gestore di eventi, a seconda se si desidera che venga eseguito in modo asincrono o sincrono.

Fondamentalmente si tratta solo di zucchero attorno alla cattura di un riferimento Control e chiamando Invoke() su di esso, ma può semplificare il codice.

Answer 4

Ho usato C# da poche settimane, ma ho riscontrato la stessa domanda su come attivare gli eventi tra i thread. Non ci sono molti esempi completi disponibili (nessuno?) Ed è stato difficile capire tutti i singoli pezzi di vari esperti. Dopo qualche tempo ho finalmente sviluppato qualcosa che funziona, quindi ho voluto condividere un esempio completo su questo thread per tutti i nuovi arrivati ​​come me. Inoltre, accolgo con favore qualsiasi consiglio o critica di esperti poiché sono abbastanza nuovo per C# e sicuramente questo può essere migliorato.

Questo è un esempio completo meno una piccola forma con 3 pulsanti e una trackbar verticale, tutti con nomi predefiniti. Crea il modulo in Designer e sovrascrivilo con la classe TestEvent che ho, quindi collega i 3 pulsanti OnClick. La barra di scorrimento può essere utilizzata per selezionare il thread su cui si desidera attivare un evento tramite i pulsanti e verrà automaticamente ridimensionato quando si modifica numThreads in Main() vuoto. Button2 invierà un evento per arrestare il thread.

La classe MyEvent può essere utilizzata in combinazione con qualsiasi classe che implementa l'interfaccia IMyEventActions. La classe che utilizza MyEvent riceverà automaticamente eventi infornati su OnSomethingHappened (...). Inoltre, la classe che crea un'istanza di MyEvent può iscriversi in modo ricorsivo ad altre classi. Gli eventi di fuoco sono facilmente raggiunti attraverso il metodo MyEvent.Fire (...).

// Create a designer form with 3 buttons and a vertical trackbar and overwrite 
//it with "TestEvent" class near bottom of code, then hook up the buttons to 
//button<1/2/3>_OnClick. Event Sibling Subscribing section explains why the 
//first 4 event threads all fire at once. 

using System; 
using System.Windows.Forms; 
using System.Threading; 
using System.Collections.Generic; 
using System.Runtime.InteropServices; 

namespace TestingEventsApplication 
{ 
    using Extensions; 
    public delegate void OnSomethingHappenedDel(MyEventArgs e); 
    public delegate void EventMarshalDel(IMyEventActions sender, MyEventArgs e); 
    static class Program 
    { 

     /// <summary> 
     /// The main entry point for the application. 
     /// </summary> 
     [STAThread] 
     static void Main() 
     { 
      Application.EnableVisualStyles(); 
      Application.SetCompatibleTextRenderingDefault(false); 
      Console.WriteLine("Thread Main is Thread#" + Thread.CurrentThread.ManagedThreadId); 

      //This controls how many threads we want to make for testing 
      int numThreads = 10; 

      QuickSync quickSync = new QuickSync(); 
      MyThread[] myThreads = new MyThread[numThreads]; 
      TestEvent GUI = new TestEvent(myThreads); 
      GUI.TrackbarVal = numThreads-1; 
      for (int i = 0; i < numThreads; i++) 
      { 
       myThreads[i] = new MyThread(); 
       Thread thread = new Thread(delegate() 
       { 
        myThreads[i].Start(quickSync); 
       }); 
       thread.Name = "Thread#" + thread.ManagedThreadId.ToString(); 
       thread.IsBackground = true; 
       thread.Start(); 
       while (!thread.IsAlive || !quickSync.Sync) { Thread.Sleep(1); } 
       myThreads[i].thread = thread; 
       Console.WriteLine(thread.Name + " is alive"); 
       quickSync.Sync = false; 
      } 

      #region Event Sibling Subscribing 
      // ********* Event Sibling Subscribing ********* 
      // Just for example, I will link Thread 0 to thread 1, then 
      // 1->2,2->3,3->4 so when thread 0 receives an event, so will 
      // thread 1, 2, 3, and 4 (Noncommutative.) 
      // Loops are perfectly acceptable and will not result in 
      // eternal events. 
      // e.g. 0->1 + 1->0 is OK, or 0->1 + 1->2 + 2->0... No problem. 
      if (numThreads > 0) 
       myThreads[0].Event.SubscribeMeTo(myThreads[1].Event); 
      //Recursively add thread 2 
      if (numThreads > 1) 
       myThreads[1].Event.SubscribeMeTo(myThreads[2].Event); 
      //Recursively add thread 3 
      if (numThreads > 2) 
       myThreads[2].Event.SubscribeMeTo(myThreads[3].Event); 
      //Recursively add thread 4 
      if (numThreads > 3) 
       myThreads[3].Event.SubscribeMeTo(myThreads[4].Event); 
      #endregion 

      Application.Run(GUI); 
     } 
    } 

    /// <summary> 
    /// Used to determine when a task is complete. 
    /// </summary> 
    public class QuickSync 
    { 
     public bool Sync 
     { 
      get 
      { 
       lock (this) 
        return sync; 
      } 
      set 
      { 
       lock (this) 
        sync = value; 
      } 
     } 

     private bool sync; 
    } 

    /// <summary> 
    /// A class representing the operating body of a Background thread. 
    /// Inherits IMyEventActions. 
    /// </summary> 
    /// <param name="m">a QuickSync boxed bool.</param> 
    public class MyThread : IMyEventActions 
    { 
     /// <summary> 
     /// An reference to the Thread object used by this thread. 
     /// </summary> 
     public Thread thread { get; set; } 

     /// <summary> 
     /// Tracks the MyEvent object used by the thread. 
     /// </summary> 
     public MyEvent Event { get; set;} 

     /// <summary> 
     /// Satisfies IMyEventActions and provides a method to implement 
     /// Event actions 
     /// </summary> 
     public void OnSomethingHappened(MyEventArgs e) 
     { 
      switch ((MyEventArgsFuncs)e.Function) 
      { 
       case MyEventArgsFuncs.Shutdown: 
        Console.WriteLine("Shutdown Event detected... " + Thread.CurrentThread.Name + " exiting"); 
        Event.Close(); 
        break; 
       case MyEventArgsFuncs.SomeOtherEvent: 
        Console.WriteLine("SomeOtherEvent Event detected on " + Thread.CurrentThread.Name); 
        break; 
       case MyEventArgsFuncs.TheLastEvent: 
        Console.WriteLine("TheLastEvent Event detected on " + Thread.CurrentThread.Name); 
        break; 
      } 
     } 

     /// <summary> 
     /// The method used by a thread starting delegate. 
     /// </summary> 
     public void Start(QuickSync quickSync) 
     { 
      //MyEvent inherits from Form which inherits from Control which is 
      //the key to this whole thing working. It is the BeginInvoke method 
      //of Control which allows us to marshal objects between threads, 
      //without it any event handlers would simply fire in the same thread 
      //which they were triggered. We don't want to see this form though 
      //so I've moved it off screen and out of the task bar 
      Event = new MyEvent(); 
      Event.MyEventSender = this; 
      Event.SomethingHappened += new EventMarshalDel(Event.EventMarshal); 
      Event.FormBorderStyle = FormBorderStyle.FixedToolWindow; 
      Event.ShowInTaskbar = false; 
      Event.StartPosition = FormStartPosition.Manual; 
      Event.Location = new System.Drawing.Point(-10000, -10000); 
      Event.Size = new System.Drawing.Size(1, 1); 
      System.Windows.Forms.Application.Idle += new EventHandler(OnApplicationIdle); 
      quickSync.Sync = true; 
      Application.Run(Event); 
     } 

     /// <summary> 
     /// The operating body of the thread. 
     /// </summary> 
     private void OnApplicationIdle(object sender, EventArgs e) 
     { 
      while (this.AppStillIdle) 
      { 
       //Do your threads work here... 
       Console.Write("."); 
       Thread.Sleep(1000); 
      } 
     } 

     /// <summary> 
     /// Monitors the Threads msg procedure to make sure we handle messages. 
     /// </summary> 
     public bool AppStillIdle 
     { 
      get 
      { 
       Win32.NativeMessage msg; 
       return !Win32.PeekMessage(out msg, IntPtr.Zero, 0, 0, 0); 
      } 
     } 
    } 

    /// <summary> 
    /// Houses all of the plumbing necessary to fire cross thread events. 
    /// </summary> 
    public class MyEvent : System.Windows.Forms.Form 
    { 
     /// <summary> 
     /// A reference to the object using this MyEvent, used during recursion. 
     /// </summary> 
     public IMyEventActions MyEventSender { get; set; } 

     /// <summary> 
     /// Lock for somethingHappened delegate access. 
     /// </summary> 
     public readonly object someEventLock = new object(); 

     /// <summary> 
     /// Public access to the event SomethingHappened with a locking 
     /// subscription mechanism for thread safety. 
     /// </summary> 
     public event EventMarshalDel SomethingHappened 
     { 
      add 
      { 
       lock (someEventLock) 
        somethingHappened += value; 
      } 
      remove 
      { 
       lock (someEventLock) //Contributes to preventing race condition 
        somethingHappened -= value; 
      } 
     } 

     /// <summary> 
     /// The trigger of MyEvent class. 
     /// </summary> 
     public void Fire(MyEventArgs e) 
     { 
      //After rigorous testing I found this was the simplest way to solve 
      //the classic event race condition. I rewired RaiseEvent and 
      //EventMarshal to increase race condition tendency, and began 
      //looping only iterating between 20 and 200 times I was able to 
      //observe the race condition every time, with this lock in place, 
      //I have iterated 10's of thousands of times without failure. 
      lock (someEventLock) 
       somethingHappened.RaiseEvent(MyEventSender, e); 
      Thread.Sleep(1); //Optional, may make things more fluid. 
     } 

     /// <summary> 
     /// The Event Marshal. 
     /// </summary> 
     public void EventMarshal(IMyEventActions sender, MyEventArgs e) 
     { 
       if (sender.Event.InvokeRequired) 
        //Without the lock in Fire() a race condition would occur 
        //here when one thread closes the MyEvent form and another 
        //tries to Invoke it. 
        sender.Event.BeginInvoke(
         new OnSomethingHappenedDel(sender.OnSomethingHappened), 
         new object[] { e }); 
       else 
        sender.OnSomethingHappened(e); 
      if (SiblingEvents.Count > 0) Recurs(e); 
     } 

     /// <summary> 
     /// Provides safe recursion and event propagation through siblings. 
     /// </summary> 
     public void Recurs(MyEventArgs e) 
     { 
      e.Event.Add(this); 
      foreach (MyEvent m in SiblingEvents) 
       lock (m.someEventLock) //Prevents Race with UnSubscribeMeTo() 
        if (!e.Event.Contains(m)) //Provides safety from Eternals 
         m.Fire(e); 
     } 

     /// <summary> 
     /// Adds sibling MyEvent classes which to fire synchronously. 
     /// </summary> 
     public void SubscribeMeTo(MyEvent m) 
     { 
      if (this != m) SiblingEvents.Add(m); 
     } 

     /// <summary> 
     /// Removes sibling MyEvent's. 
     /// </summary> 
     public void UnSubscribeMeTo(MyEvent m) 
     { 
      lock (m.someEventLock) //Prevents race condition with Recurs() 
       if (SiblingEvents.Contains(m)) SiblingEvents.Remove(m); 
     } 

     protected override void OnFormClosing(FormClosingEventArgs e) 
     { 
      SomethingHappened -= somethingHappened; 
      base.OnFormClosing(e); 
     } 

     /// <summary> 
     /// Delegate backing the SomethingHappened event. 
     /// </summary> 
     private EventMarshalDel somethingHappened; 

     /// <summary> 
     /// A list of siblings to Eventcast. 
     /// </summary> 
     private List<MyEvent> SiblingEvents = new List<MyEvent>(); 
    } 

    /// <summary> 
    /// The interface used by MyThread to enlist OnSomethingHappened arbiter. 
    /// </summary> 
    public interface IMyEventActions 
    { 
     void OnSomethingHappened(MyEventArgs e); 
     MyEvent Event { get; set; } 
    } 

    public enum MyEventArgsFuncs : int 
    { 
     Shutdown = 0, 
     SomeOtherEvent, 
     TheLastEvent 
    }; 

    /// <summary> 
    /// Uses a string-referable enum to target functions handled 
    /// by OnSomethingHappened. 
    /// </summary> 
    public class MyEventArgs : EventArgs 
    { 
     public int Function { get; set; } 
     public List<MyEvent> Event = new List<MyEvent>(); 
     public MyEventArgs(string s) 
     { 
      this.Function = (int)Enum.Parse(typeof(MyEventArgsFuncs), s); 
     } 
    } 

    /// <summary> 
    /// This is a form with 3 buttons and a trackbar on it. 
    /// </summary> 
    /// <param name="m">An array of MyThread objects.</param> 
    // Create a designer form with 3 buttons and a trackbar and overwrite it 
    // with this, then hook up the buttons to button<1/2/3>_OnClick. 
    public partial class TestEvent : Form 
    { 
     public TestEvent() 
     { 
      InitializeComponent(); 
     } 

     public TestEvent(MyThread[] t) 
      : this() 
     { 
      myThreads = t; 
     } 

     /// <summary> 
     /// This button will fire a test event, which will write to the 
     /// console via OnSomethingHappened in another thread. 
     /// </summary> 
     private void button1_OnClick(object sender, EventArgs e) 
     { 
      Console.WriteLine("Firing SomeOtherEvent from Thread#" + Thread.CurrentThread.ManagedThreadId + " (Main)"); 
      myThreads[TrackbarVal].Event.Fire(new MyEventArgs("SomeOtherEvent")); 
     } 

     /// <summary> 
     /// This button will fire an event, which remotely shut down the 
     /// myEvent form and kill the thread. 
     /// </summary> 
     private void button2_OnClick(object sender, EventArgs e) 
     { 
      Console.WriteLine("Firing Shutdown event from Thread#" + Thread.CurrentThread.ManagedThreadId + " (Main)"); 
      myThreads[TrackbarVal].Event.Fire(new MyEventArgs("Shutdown")); 
     } 

     /// <summary> 
     /// This button will fire TheLastEvent, which will write to the 
     /// console via OnSomethingHappened in another thread. 
     /// </summary> 
     private void button3_OnClick(object sender, System.EventArgs e) 
     { 
      Console.WriteLine("Firing TheLastEvent from Thread#" + Thread.CurrentThread.ManagedThreadId + " (Main)"); 
      myThreads[TrackbarVal].Event.Fire(new MyEventArgs("TheLastEvent")); 
     } 

     public int TrackbarVal 
     { 
      get { return this.trackBar1.Value; } 
      set { this.trackBar1.Maximum = value; } 
     } 

     private MyThread[] myThreads; 
    } 

    /// <summary> 
    /// Stores Win32 API's. 
    /// </summary> 
    public class Win32 
    { 
     /// <summary> 
     /// Used to determine if there are messages waiting 
     /// </summary> 
     [System.Security.SuppressUnmanagedCodeSecurity] 
     [return: MarshalAs(UnmanagedType.Bool)] 
     [DllImport("User32.dll", CharSet = CharSet.Auto, SetLastError = true)] 
     public static extern bool PeekMessage(out NativeMessage message, IntPtr handle, uint filterMin, uint filterMax, uint flags); 

     [StructLayout(LayoutKind.Sequential)] 
     public struct NativeMessage 
     { 
      public IntPtr handle; 
      public uint msg; 
      public IntPtr wParam; 
      public IntPtr lParam; 
      public uint time; 
      public System.Drawing.Point p; 
     } 
    } 
} 

namespace Extensions 
{ 
    using System; 
    using TestingEventsApplication; 

    /// <summary> 
    /// An extension method to null test for any OnSomethingHappened 
    /// event handlers. 
    /// </summary> 
    public static class Extension 
    { 
     public static void RaiseEvent(this EventMarshalDel @event, IMyEventActions sender, MyEventArgs e) 
     { 
      if (@event != null) 
       @event(sender, e); 
     } 
    } 
}