Criando segmentos e passar dados em time de início

Quando um processo do sistema operacional é criado, o sistema operacional injeta uma thread para executar código nesse processo, incluindo qualquer domínio do aplicativo original.Desse ponto em diante, os domínios de aplicativo podem ser criados e destruídos sem nenhum thread do sistema operacional necessariamente que está sendo criado ou destruído.Se o código que está sendo executado é código gerenciado e, em seguida, um Thread objeto para o thread executando em um domínio do aplicativo corrente pode ser obtido Recuperando o estático CurrentThread propriedade do tipo Thread. Este tópico descreve a criação do thread e discute as alternativas para a passagem de dados para o procedimento de thread.

Criar um thread

Criando um novo Thread objeto cria um novo thread gerenciado. The Thread classe tem construtores que utilizam um ThreadStart delegar ou um ParameterizedThreadStart delegar; o delegado encapsula o método que é invocado, o novo thread quando você telefonar o Start método. De chamadaStart mais de uma vez, faz com que um ThreadStateException para ser lançada.

The Start método retorna imediatamente, muitas vezes antes do novo thread realmente foi iniciado. Você pode usar o ThreadState e IsAlive propriedades para determinar o estado do thread em qualquer um dado momento, mas essas propriedades nunca devem ser usado para sincronizar as atividades de thread s.

Observação:
Quando um thread for iniciado, não é necessário manter uma referência para o Thread objeto. O thread continua a executar até o thread procedimento termina.

O exemplo de código a seguir cria dois novos threads para telefonar instância e métodos estático em outro objeto.

Imports System
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 'InstanceMethod

    Public Shared Sub 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.")
    End Sub 'StaticMethod
End Class 'ServerClass

Public Class Simple

    Public Shared Sub Main() 
        Console.WriteLine("Thread Simple Sample")

        Dim serverObject As New ServerClass()

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

        ' Start the thread.
        StaticCaller.Start()

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

    End Sub 'Main
End Class 'Simple

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 int Main(String[] args)
    {
        Console.WriteLine("Thread Simple Sample");

        ServerClass serverObject = new ServerClass();

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

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

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

        return 0;
    }
}

using namespace System;
using namespace System::Threading;

public ref class ServerClass
{
public:

    // The method that will be called when the thread is started.
    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.");
    }

    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.");
    }
};

void main()
{
    Console::WriteLine("Thread Simple Sample");

    ServerClass^ serverObject = gcnew ServerClass();

    // Create the thread object, passing in a ThreadStart delegate
    // representing an instance of ServerClass and the 
    // ServerClass::InstanceMethod method.
    Thread^ InstanceCaller = gcnew Thread(
        gcnew ThreadStart(serverObject, &ServerClass::InstanceMethod));

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

    Console::WriteLine("The main thread has " 
        + "started the new InstanceMethod thread.");

    // Create the thread object, passing in a ThreadStart delegate 
    // representing the static ServerClass::StaticMethod method.
    Thread^ StaticCaller = gcnew Thread(
        gcnew ThreadStart(&ServerClass::StaticMethod));

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

    Console::WriteLine("The main thread has called "
        + "the new StaticMethod thread.");
}

Passando dados para threads e recuperando dados de threads

No .NET estrutura versão 2.0, a ParameterizedThreadStart delegado oferece uma maneira fácil de passar um objeto que contém dados a um thread quando você chama o Thread.Start sobrecarga de método. See ParameterizedThreadStart Para obter um exemplo de código.

Usando o ParameterizedThreadStart delegado não é uma maneira de fortemente tipado para passar dados, porque o Thread.Start sobrecarga de método aceita qualquer objeto. Uma alternativa é encapsular o procedimento de thread e os dados em uma classe auxiliar e usar o ThreadStart delegado para executar o procedimento de thread. Essa técnica é mostrada na exemplos duas de código a seguir.

Nenhuma dessas delegados tem um valor retornado, porque não há nenhum lugar para retornar os dados de uma telefonar assíncrono.Para recuperar sistema autônomo resultados de um método de thread, você pode usar um método de retorno de chamada, conforme demonstrado no segundo exemplo de código.

Imports System
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 value As Integer

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

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

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 value;

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

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

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

        // Create a thread to execute the task, and then
        // start the thread.
        Thread t = new Thread(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.");  
    }
}

using namespace System;
using namespace System::Threading;

// The ThreadWithState class contains the information needed for
// a task, and the method that executes the task.
//
public ref class ThreadWithState 
{
private:
    // State information used in the task.
    String^ boilerplate;
    int value;

public:
    // The constructor obtains the state information.
    ThreadWithState(String^ text, int number) 
    {
        boilerplate = text;
        value = number;
    }

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

// Entry point for the example.
//
void main() 
{
    // Supply the state information required by the task.
    ThreadWithState^ tws = gcnew ThreadWithState(
        "This report displays the number {0}.", 42);

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

Recuperando dados com métodos de retorno de chamada

O exemplo a seguir demonstra um método de retorno de chamada que recupera dados de um segmento.O construtor da classe que contém os dados e o método de thread também aceita um delegado que representa o método de retorno de chamada; antes do método de thread, ele invoca o delegado de retorno de chamada.

Imports System
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 value 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(ByVal text As String, ByVal number As Integer, _
                   ByVal callbackDelegate As ExampleCallback)
        boilerplate = text
        value = 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, value) 
        If Not callback Is Nothing Then callback(1)
    End Sub
End Class

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

' 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, _
            New ExampleCallback(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

    ' The callback method must match the signature of the
    ' callback delegate.
    '
    Public Shared Sub ResultCallback(ByVal lineCount As Integer)
        Console.WriteLine("Independent task printed {0} lines.", _
            lineCount)  
    End Sub
End Class

using System;
using 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 string boilerplate;
    private int value;

    // 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 ThreadWithState(string text, int number, 
        ExampleCallback callbackDelegate) 
    {
        boilerplate = text;
        value = 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, value);
        if (callback != null)
            callback(1);
    }
}

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

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

        Thread t = new Thread(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 {0} lines.", lineCount);
    }
}

using namespace System;
using namespace System::Threading;

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

// 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 ref class ThreadWithState 
{
private:
    // State information used in the task.
    String^ boilerplate;
    int value;

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

public:
    // The constructor obtains the state information and the
    // callback delegate.
    ThreadWithState(String^ text, int number, 
        ExampleCallback^ callbackDelegate)  
    {
        boilerplate = text;
        value = 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.
    void ThreadProc() 
    {
        Console::WriteLine(boilerplate, value); 
        if (callback != nullptr)
            callback(1);
    }
};

public ref class Example
{
public:
    static void Demo()
    {
        // Supply the state information required by the task.
        ThreadWithState^ tws = gcnew ThreadWithState(
            "This report displays the number {0}.",
            42,
            gcnew ExampleCallback(&Example::ResultCallback)
        );

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

private:
    // The callback method must match the signature of the
    // callback delegate.
    //
    static void ResultCallback(int lineCount) 
    {
        Console::WriteLine(
            "Independent task printed {0} lines.", lineCount);
    }
};

// Entry point for the example.
//
void main() 
{
    Example::Demo();
}

Consulte também

Referência

Thread

ThreadStart

ParameterizedThreadStart

Thread.Start

Outros recursos

Threads gerenciadas

Usando threads e Threading