Erstellen von Threads und Übergeben von Daten zum Startzeitpunkt

Wenn ein Betriebssystemprozess erstellt wird, fügt das Betriebssystem einen Thread ein, um Code in diesem Prozess auszuführen, einschließlich einer ursprünglichen Anwendungsdomäne. Ab diesem Zeitpunkt können Anwendungsdomänen erstellt und zerstört werden, ohne dass unbedingt Betriebssystemthreads erstellt oder zerstört werden. Wenn der ausgeführte Code verwalteter Code ist, kann ein Thread Objekt für den Thread, der in der aktuellen Anwendungsdomäne ausgeführt wird, abgerufen werden, indem die statische CurrentThread Eigenschaft des Typs Threadabgerufen wird. In diesem Thema wird die Threaderstellung beschrieben und Alternativen zum Übergeben von Daten an die Threadprozedur erläutert.

Erstellen eines Threads

Durch das Erstellen eines neuen Thread Objekts wird ein neuer verwalteter Thread erstellt. Die Thread Klasse verfügt über Konstruktoren, die einen ThreadStart Delegat oder einen ParameterizedThreadStart Delegaten annehmen. Der Delegat umschließt die Methode, die vom neuen Thread aufgerufen wird, wenn Sie die Start Methode aufrufen. Das Aufrufen Start mehrerer Aufrufe bewirkt, dass ein ThreadStateException Auslösen ausgelöst wird.

Die Start Methode gibt sofort zurück, oft bevor der neue Thread tatsächlich gestartet wurde. Sie können die ThreadState Und-Eigenschaften IsAlive verwenden, um den Status des Threads zu einem beliebigen Zeitpunkt zu bestimmen, aber diese Eigenschaften sollten niemals zum Synchronisieren der Aktivitäten von Threads verwendet werden.

Hinweis

Nachdem ein Thread gestartet wurde, ist es nicht erforderlich, einen Verweis auf das Thread Objekt beizubehalten. Der Thread wird weiterhin ausgeführt, bis die Threadprozedur endet.

Im folgenden Codebeispiel werden zwei neue Threads zum Aufrufen von Instanzen und statischen Methoden für ein anderes Objekt erstellt.

using System;
using System.Threading;

public class ServerClass
{
    // The method that will be called when the thread is started.
    public void InstanceMethod()
    {
        Console.WriteLine(
            "ServerClass.InstanceMethod is running on another thread.");

        // Pause for a moment to provide a delay to make
        // threads more apparent.
        Thread.Sleep(3000);
        Console.WriteLine(
            "The instance method called by the worker thread has ended.");
    }

    public static void StaticMethod()
    {
        Console.WriteLine(
            "ServerClass.StaticMethod is running on another thread.");

        // Pause for a moment to provide a delay to make
        // threads more apparent.
        Thread.Sleep(5000);
        Console.WriteLine(
            "The static method called by the worker thread has ended.");
    }
}

public class Simple
{
    public static void Main()
    {
        ServerClass serverObject = new ServerClass();

        // Create the thread object, passing in the
        // serverObject.InstanceMethod method using a
        // ThreadStart delegate.
        Thread InstanceCaller = new(new ThreadStart(serverObject.InstanceMethod));

        // Start the thread.
        InstanceCaller.Start();

        Console.WriteLine("The Main() thread calls this after "
            + "starting the new InstanceCaller thread.");

        // Create the thread object, passing in the
        // serverObject.StaticMethod method using a
        // ThreadStart delegate.
        Thread StaticCaller = new(new ThreadStart(ServerClass.StaticMethod));

        // Start the thread.
        StaticCaller.Start();

        Console.WriteLine("The Main() thread calls this after "
            + "starting the new StaticCaller thread.");
    }
}
// The example displays the output like the following:
//    The Main() thread calls this after starting the new InstanceCaller thread.
//    The Main() thread calls this after starting the new StaticCaller thread.
//    ServerClass.StaticMethod is running on another thread.
//    ServerClass.InstanceMethod is running on another thread.
//    The instance method called by the worker thread has ended.
//    The static method called by the worker thread has ended.

Imports System.Threading

Public class ServerClass
    ' The method that will be called when the thread is started.
    Public Sub InstanceMethod()
        Console.WriteLine(
            "ServerClass.InstanceMethod is running on another thread.")

        ' Pause for a moment to provide a delay to make
        ' threads more apparent.
        Thread.Sleep(3000)
        Console.WriteLine(
            "The instance method called by the worker thread has ended.")
    End Sub

    Public Shared Sub SharedMethod()
        Console.WriteLine(
            "ServerClass.SharedMethod is running on another thread.")

        ' Pause for a moment to provide a delay to make
        ' threads more apparent.
        Thread.Sleep(5000)
        Console.WriteLine(
            "The Shared method called by the worker thread has ended.")
    End Sub
End Class

Public class Simple
    Public Shared Sub Main()
        Dim serverObject As New ServerClass()

        ' Create the thread object, passing in the
        ' serverObject.InstanceMethod method using a
        ' ThreadStart delegate.
        Dim InstanceCaller As New Thread(AddressOf serverObject.InstanceMethod)

        ' Start the thread.
        InstanceCaller.Start()

        Console.WriteLine("The Main() thread calls this after " _
            + "starting the new InstanceCaller thread.")

        ' Create the thread object, passing in the
        ' serverObject.SharedMethod method using a
        ' ThreadStart delegate.
        Dim SharedCaller As New Thread( _
            New ThreadStart(AddressOf ServerClass.SharedMethod))

        ' Start the thread.
        SharedCaller.Start()

        Console.WriteLine("The Main() thread calls this after " _
            + "starting the new SharedCaller thread.")
    End Sub
End Class
' The example displays output like the following:
'    The Main() thread calls this after starting the new InstanceCaller thread.
'    The Main() thread calls this after starting the new StaticCaller thread.
'    ServerClass.StaticMethod is running on another thread.
'    ServerClass.InstanceMethod is running on another thread.
'    The instance method called by the worker thread has ended.
'    The static method called by the worker thread has ended.

Übergeben von Daten an Threads

Der ParameterizedThreadStart Delegat bietet eine einfache Möglichkeit, ein Objekt, das Daten enthält, an einen Thread zu übergeben, wenn Sie aufrufen Thread.Start(Object). Ein Codebeispiel finden Sie ParameterizedThreadStart unter .

Die Verwendung des ParameterizedThreadStart Delegaten ist keine typsichere Methode zum Übergeben von Daten, da die Thread.Start(Object) Methode jedes Objekt akzeptiert. Eine Alternative besteht darin, die Threadprozedur und die Daten in einer Hilfsklasse zu kapseln und den ThreadStart Delegaten zum Ausführen der Threadprozedur zu verwenden. Das folgende Beispiel veranschaulicht diese Technik:

using System;
using System.Threading;

// The ThreadWithState class contains the information needed for
// a task, and the method that executes the task.
//
public class ThreadWithState
{
    // State information used in the task.
    private string _boilerplate;
    private int _numberValue;

    // The constructor obtains the state information.
    public ThreadWithState(string text, int number)
    {
        _boilerplate = text;
        _numberValue = number;
    }

    // The thread procedure performs the task, such as formatting
    // and printing a document.
    public void ThreadProc()
    {
        Console.WriteLine(_boilerplate, _numberValue);
    }
}

// Entry point for the example.
public class Example
{
    public static void Main()
    {
        // Supply the state information required by the task.
        ThreadWithState tws = new("This report displays the number {0}.", 42);

        // Create a thread to execute the task, and then
        // start the thread.
        Thread t = new(new ThreadStart(tws.ThreadProc));
        t.Start();
        Console.WriteLine("Main thread does some work, then waits.");
        t.Join();
        Console.WriteLine(
            "Independent task has completed; main thread ends.");
    }
}

// The example displays the following output:
//       Main thread does some work, then waits.
//       This report displays the number 42.
//       Independent task has completed; main thread ends.

Imports System.Threading

' The ThreadWithState class contains the information needed for
' a task, and the method that executes the task.
Public Class ThreadWithState
    ' State information used in the task.
    Private boilerplate As String
    Private numberValue As Integer

    ' The constructor obtains the state information.
    Public Sub New(text As String, number As Integer)
        boilerplate = text
        numberValue = number
    End Sub

    ' The thread procedure performs the task, such as formatting
    ' and printing a document.
    Public Sub ThreadProc()
        Console.WriteLine(boilerplate, numberValue)
    End Sub
End Class

' Entry point for the example.
'
Public Class Example
    Public Shared Sub Main()
        ' Supply the state information required by the task.
        Dim tws As New ThreadWithState( _
            "This report displays the number {0}.", 42)

        ' Create a thread to execute the task, and then
        ' start the thread.
        Dim t As New Thread(New ThreadStart(AddressOf tws.ThreadProc))
        t.Start()
        Console.WriteLine("Main thread does some work, then waits.")
        t.Join()
        Console.WriteLine( _
            "Independent task has completed main thread ends.")
    End Sub
End Class
' The example displays the following output:
'       Main thread does some work, then waits.
'       This report displays the number 42.
'       Independent task has completed; main thread ends.

Weder noch Stellvertretung ThreadStartParameterizedThreadStart hat einen Rückgabewert, da keine Stelle zum Zurückgeben der Daten aus einem asynchronen Aufruf vorhanden ist. Zum Abrufen der Ergebnisse einer Threadmethode können Sie eine Rückrufmethode verwenden, wie im nächsten Abschnitt gezeigt.

Abrufen von Daten aus Threads mit Rückrufmethoden

Das folgende Beispiel veranschaulicht eine Rückrufmethode, die Daten aus einem Thread abruft. Der Konstruktor für die Klasse, die die Daten enthält, und die Threadmethode akzeptiert auch einen Delegaten, der die Rückrufmethode darstellt; bevor die Threadmethode endet, ruft sie den Rückrufdelegat auf.

using System;
using System.Threading;

// The ThreadWithState2 class contains the information needed for
// a task, the method that executes the task, and a delegate
// to call when the task is complete.
public class ThreadWithState2
{
    // State information used in the task.
    private string _boilerplate;
    private int _numberValue;

    // Delegate used to execute the callback method when the
    // task is complete.
    private ExampleCallback _callback;

    // The constructor obtains the state information and the
    // callback delegate.
    public ThreadWithState2(string text, int number,
        ExampleCallback callbackDelegate)
    {
        _boilerplate = text;
        _numberValue = number;
        _callback = callbackDelegate;
    }

    // The thread procedure performs the task, such as
    // formatting and printing a document, and then invokes
    // the callback delegate with the number of lines printed.
    public void ThreadProc()
    {
        Console.WriteLine(_boilerplate, _numberValue);
        _callback?.Invoke(1);
    }
}

// Delegate that defines the signature for the callback method.
public delegate void ExampleCallback(int lineCount);

// Entry point for the example.
public class Example2
{
    public static void Main()
    {
        // Supply the state information required by the task.
        ThreadWithState2 tws = new(
            "This report displays the number {0}.",
            42,
            new ExampleCallback(ResultCallback)
        );

        Thread t = new(new ThreadStart(tws.ThreadProc));
        t.Start();
        Console.WriteLine("Main thread does some work, then waits.");
        t.Join();
        Console.WriteLine(
            "Independent task has completed; main thread ends.");
    }

    // The callback method must match the signature of the
    // callback delegate.
    public static void ResultCallback(int lineCount)
    {
        Console.WriteLine($"Independent task printed {lineCount} lines.");
    }
}

// The example displays the following output:
//       Main thread does some work, then waits.
//       This report displays the number 42.
//       Independent task printed 1 lines.
//       Independent task has completed; main thread ends.

Imports System.Threading

' The ThreadWithState class contains the information needed for
' a task, the method that executes the task, and a delegate
' to call when the task is complete.
Public Class ThreadWithState
    ' State information used in the task.
    Private boilerplate As String
    Private numberValue As Integer

    ' Delegate used to execute the callback method when the
    ' task is complete.
    Private callback As ExampleCallback

    ' The constructor obtains the state information and the
    ' callback delegate.
    Public Sub New(text As String, number As Integer, _
        callbackDelegate As ExampleCallback)
        boilerplate = text
        numberValue = number
        callback = callbackDelegate
    End Sub

    ' The thread procedure performs the task, such as
    ' formatting and printing a document, and then invokes
    ' the callback delegate with the number of lines printed.
    Public Sub ThreadProc()
        Console.WriteLine(boilerplate, numberValue)
        If Not (callback Is Nothing) Then
            callback(1)
        End If
    End Sub
End Class

' Delegate that defines the signature for the callback method.
'
Public Delegate Sub ExampleCallback(lineCount As Integer)

Public Class Example
    Public Shared Sub Main()
        ' Supply the state information required by the task.
        Dim tws As New ThreadWithState( _
            "This report displays the number {0}.", _
            42, _
            AddressOf ResultCallback)

        Dim t As New Thread(AddressOf tws.ThreadProc)
        t.Start()
        Console.WriteLine("Main thread does some work, then waits.")
        t.Join()
        Console.WriteLine( _
            "Independent task has completed; main thread ends.")
    End Sub

    Public Shared Sub ResultCallback(lineCount As Integer)
        Console.WriteLine( _
            "Independent task printed {0} lines.", lineCount)
    End Sub
End Class
' The example displays the following output:
'       Main thread does some work, then waits.
'       This report displays the number 42.
'       Independent task printed 1 lines.
'       Independent task has completed; main thread ends.

Siehe auch

• Thread
• ThreadStart
• ParameterizedThreadStart
• Thread.Start
• Einfädelnd
• Verwenden von Threads und Threading