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Como: Um componente que oferece suporte ao implementar o padrão assíncrono baseado em evento

O exemplo de código a seguir implementa um componente com um método assíncrono, de acordo com para o padrão assíncrono baseado em evento Visão geral sobre. O componente é uma calculadora número primo, que usa o algoritmo Sieve de Eratosthenes para determinar se um número é principal ou compostos.

Há suporte abrangente para este recurso no Visual Studio.

Para um cliente de exemplo que usa o PrimeNumberCalculator componente, consulte Como: Implementar um cliente do padrão assíncrono baseado em evento.

Exemplo

Imports System
Imports System.Collections
Imports System.Collections.Specialized
Imports System.ComponentModel
Imports System.Drawing
Imports System.Globalization
Imports System.Threading
Imports System.Windows.Forms


...



Public Delegate Sub ProgressChangedEventHandler( _
    ByVal e As ProgressChangedEventArgs)

Public Delegate Sub CalculatePrimeCompletedEventHandler( _
    ByVal sender As Object, _
    ByVal e As CalculatePrimeCompletedEventArgs)

' This class implements the Event-based Asynchronous Pattern.
' It asynchronously computes whether a number is prime or
' composite (not prime).
Public Class PrimeNumberCalculator
    Inherits System.ComponentModel.Component

    Private Delegate Sub WorkerEventHandler( _
    ByVal numberToCheck As Integer, _
    ByVal asyncOp As AsyncOperation)

    Private onProgressReportDelegate As SendOrPostCallback
    Private onCompletedDelegate As SendOrPostCallback

    Private userStateToLifetime As New HybridDictionary()

    Private components As System.ComponentModel.Container = Nothing

    '''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
#Region "Public events"

    Public Event ProgressChanged _
        As ProgressChangedEventHandler
    Public Event CalculatePrimeCompleted _
        As CalculatePrimeCompletedEventHandler

#End Region

    '''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
#Region "Construction and destruction"


    Public Sub New(ByVal container As System.ComponentModel.IContainer)

        container.Add(Me)
        InitializeComponent()

        InitializeDelegates()

    End Sub


    Public Sub New()

        InitializeComponent()

        InitializeDelegates()

    End Sub


    Protected Overridable Sub InitializeDelegates()
        onProgressReportDelegate = _
            New SendOrPostCallback(AddressOf ReportProgress)
        onCompletedDelegate = _
            New SendOrPostCallback(AddressOf CalculateCompleted)
    End Sub


    Protected Overrides Sub Dispose(ByVal disposing As Boolean)
        If disposing Then
            If (components IsNot Nothing) Then
                components.Dispose()
            End If
        End If
        MyBase.Dispose(disposing)

    End Sub

#End Region

    '''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
#Region "Implementation"


    ' This method starts an asynchronous calculation. 
    ' First, it checks the supplied task ID for uniqueness.
    ' If taskId is unique, it creates a new WorkerEventHandler 
    ' and calls its BeginInvoke method to start the calculation.
    Public Overridable Sub CalculatePrimeAsync( _
        ByVal numberToTest As Integer, _
        ByVal taskId As Object)

        ' Create an AsyncOperation for taskId.
        Dim asyncOp As AsyncOperation = _
            AsyncOperationManager.CreateOperation(taskId)

        ' Multiple threads will access the task dictionary,
        ' so it must be locked to serialize access.
        SyncLock userStateToLifetime.SyncRoot
            If userStateToLifetime.Contains(taskId) Then
                Throw New ArgumentException( _
                    "Task ID parameter must be unique", _
                    "taskId")
            End If

            userStateToLifetime(taskId) = asyncOp
        End SyncLock

        ' Start the asynchronous operation.
        Dim workerDelegate As New WorkerEventHandler( _
            AddressOf CalculateWorker)

        workerDelegate.BeginInvoke( _
            numberToTest, _
            asyncOp, _
            Nothing, _
            Nothing)

    End Sub

    ' Utility method for determining if a 
    ' task has been canceled.
    Private Function TaskCanceled(ByVal taskId As Object) As Boolean
        Return (userStateToLifetime(taskId) Is Nothing)
    End Function

    ' This method cancels a pending asynchronous operation.
    Public Sub CancelAsync(ByVal taskId As Object)

        Dim obj As Object = userStateToLifetime(taskId)
        If (obj IsNot Nothing) Then

            SyncLock userStateToLifetime.SyncRoot

                userStateToLifetime.Remove(taskId)

            End SyncLock

        End If

    End Sub

    ' This method performs the actual prime number computation.
    ' It is executed on the worker thread.
    Private Sub CalculateWorker( _
        ByVal numberToTest As Integer, _
        ByVal asyncOp As AsyncOperation)

        Dim prime As Boolean = False
        Dim firstDivisor As Integer = 1
        Dim exc As Exception = Nothing

        ' Check that the task is still active.
        ' The operation may have been canceled before
        ' the thread was scheduled.
        If Not Me.TaskCanceled(asyncOp.UserSuppliedState) Then

            Try
                ' Find all the prime numbers up to the
                ' square root of numberToTest.
                Dim primes As ArrayList = BuildPrimeNumberList( _
                    numberToTest, asyncOp)

                ' Now we have a list of primes less than 
                'numberToTest.
                prime = IsPrime( _
                    primes, _
                    numberToTest, _
                    firstDivisor)

            Catch ex As Exception
                exc = ex
            End Try

        End If

        Me.CompletionMethod( _
            numberToTest, _
            firstDivisor, _
            prime, _
            exc, _
            TaskCanceled(asyncOp.UserSuppliedState), _
            asyncOp)

    End Sub

    ' This method computes the list of prime numbers used by the
    ' IsPrime method.
    Private Function BuildPrimeNumberList( _
        ByVal numberToTest As Integer, _
        ByVal asyncOp As AsyncOperation) As ArrayList

        Dim e As ProgressChangedEventArgs = Nothing
        Dim primes As New ArrayList
        Dim firstDivisor As Integer
        Dim n As Integer = 5

        ' Add the first prime numbers.
        primes.Add(2)
        primes.Add(3)

        ' Do the work.
        While n < numberToTest And _
            Not Me.TaskCanceled(asyncOp.UserSuppliedState)

            If IsPrime(primes, n, firstDivisor) Then
                ' Report to the client that you found a prime.
                e = New CalculatePrimeProgressChangedEventArgs( _
                    n, _
                    CSng(n) / CSng(numberToTest) * 100, _
                    asyncOp.UserSuppliedState)

                asyncOp.Post(Me.onProgressReportDelegate, e)

                primes.Add(n)

                ' Yield the rest of this time slice.
                Thread.Sleep(0)
            End If

            ' Skip even numbers.
            n += 2

        End While

        Return primes

    End Function


    ' This method tests n for primality against the list of 
    ' prime numbers contained in the primes parameter.
    Private Function IsPrime( _
        ByVal primes As ArrayList, _
        ByVal n As Integer, _
        ByRef firstDivisor As Integer) As Boolean

        Dim foundDivisor As Boolean = False
        Dim exceedsSquareRoot As Boolean = False

        Dim i As Integer = 0
        Dim divisor As Integer = 0
        firstDivisor = 1

        ' Stop the search if:
        ' there are no more primes in the list,
        ' there is a divisor of n in the list, or
        ' there is a prime that is larger than 
        ' the square root of n.
        While i < primes.Count AndAlso _
            Not foundDivisor AndAlso _
            Not exceedsSquareRoot

            ' The divisor variable will be the smallest prime number 
            ' not yet tried.
            divisor = primes(i)
            i = i + 1

            ' Determine whether the divisor is greater than the 
            ' square root of n.
            If divisor * divisor > n Then
                exceedsSquareRoot = True
                ' Determine whether the divisor is a factor of n.
            ElseIf n Mod divisor = 0 Then
                firstDivisor = divisor
                foundDivisor = True
            End If
        End While

        Return Not foundDivisor

    End Function


    ' This method is invoked via the AsyncOperation object,
    ' so it is guaranteed to be executed on the correct thread.
    Private Sub CalculateCompleted(ByVal operationState As Object)
        Dim e As CalculatePrimeCompletedEventArgs = operationState

        OnCalculatePrimeCompleted(e)

    End Sub


    ' This method is invoked via the AsyncOperation object,
    ' so it is guaranteed to be executed on the correct thread.
    Private Sub ReportProgress(ByVal state As Object)
        Dim e As ProgressChangedEventArgs = state

        OnProgressChanged(e)

    End Sub

    Protected Sub OnCalculatePrimeCompleted( _
        ByVal e As CalculatePrimeCompletedEventArgs)

        RaiseEvent CalculatePrimeCompleted(Me, e)

    End Sub


    Protected Sub OnProgressChanged( _
        ByVal e As ProgressChangedEventArgs)

        RaiseEvent ProgressChanged(e)

    End Sub


    ' This is the method that the underlying, free-threaded 
    ' asynchronous behavior will invoke.  This will happen on
    '  an arbitrary thread.
    Private Sub CompletionMethod( _
        ByVal numberToTest As Integer, _
        ByVal firstDivisor As Integer, _
        ByVal prime As Boolean, _
        ByVal exc As Exception, _
        ByVal canceled As Boolean, _
        ByVal asyncOp As AsyncOperation)

        ' If the task was not previously canceled,
        ' remove the task from the lifetime collection.
        If Not canceled Then
            SyncLock userStateToLifetime.SyncRoot
                userStateToLifetime.Remove(asyncOp.UserSuppliedState)
            End SyncLock
        End If

        ' Package the results of the operation in a 
        ' CalculatePrimeCompletedEventArgs.
        Dim e As New CalculatePrimeCompletedEventArgs( _
            numberToTest, _
            firstDivisor, _
            prime, _
            exc, _
            canceled, _
            asyncOp.UserSuppliedState)

        ' End the task. The asyncOp object is responsible 
        ' for marshaling the call.
        asyncOp.PostOperationCompleted(onCompletedDelegate, e)

        ' Note that after the call to PostOperationCompleted, asyncOp
        ' is no longer usable, and any attempt to use it will cause.
        ' an exception to be thrown.

    End Sub

#End Region


    Private Sub InitializeComponent()

    End Sub


End Class

Public Class CalculatePrimeProgressChangedEventArgs
    Inherits ProgressChangedEventArgs
    Private latestPrimeNumberValue As Integer = 1


    Public Sub New( _
        ByVal latestPrime As Integer, _
        ByVal progressPercentage As Integer, _
        ByVal UserState As Object)

        MyBase.New(progressPercentage, UserState)
        Me.latestPrimeNumberValue = latestPrime

    End Sub

    Public ReadOnly Property LatestPrimeNumber() As Integer
        Get
            Return latestPrimeNumberValue
        End Get
    End Property
End Class

Public Class CalculatePrimeCompletedEventArgs
    Inherits AsyncCompletedEventArgs
    Private numberToTestValue As Integer = 0
    Private firstDivisorValue As Integer = 1
    Private isPrimeValue As Boolean


    Public Sub New( _
    ByVal numberToTest As Integer, _
    ByVal firstDivisor As Integer, _
    ByVal isPrime As Boolean, _
    ByVal e As Exception, _
    ByVal canceled As Boolean, _
    ByVal state As Object)

        MyBase.New(e, canceled, state)
        Me.numberToTestValue = numberToTest
        Me.firstDivisorValue = firstDivisor
        Me.isPrimeValue = isPrime

    End Sub


    Public ReadOnly Property NumberToTest() As Integer
        Get
            ' Raise an exception if the operation failed 
            ' or was canceled.
            RaiseExceptionIfNecessary()

            ' If the operation was successful, return 
            ' the property value.
            Return numberToTestValue
        End Get
    End Property


    Public ReadOnly Property FirstDivisor() As Integer
        Get
            ' Raise an exception if the operation failed 
            ' or was canceled.
            RaiseExceptionIfNecessary()

            ' If the operation was successful, return 
            ' the property value.
            Return firstDivisorValue
        End Get
    End Property


    Public ReadOnly Property IsPrime() As Boolean
        Get
            ' Raise an exception if the operation failed 
            ' or was canceled.
            RaiseExceptionIfNecessary()

            ' If the operation was successful, return 
            ' the property value.
            Return isPrimeValue
        End Get
    End Property
End Class
using System;
using System.Collections;
using System.Collections.Specialized;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Globalization;
using System.Threading;
using System.Windows.Forms;


...



/////////////////////////////////////////////////////////////
#region PrimeNumberCalculator Implementation

public delegate void ProgressChangedEventHandler(
    ProgressChangedEventArgs e);

public delegate void CalculatePrimeCompletedEventHandler(
    object sender,
    CalculatePrimeCompletedEventArgs e);

// This class implements the Event-based Asynchronous Pattern.
// It asynchronously computes whether a number is prime or
// composite (not prime).
public class PrimeNumberCalculator : Component
{
    private delegate void WorkerEventHandler(
        int numberToCheck,
        AsyncOperation asyncOp);

    private SendOrPostCallback onProgressReportDelegate;
    private SendOrPostCallback onCompletedDelegate;

    private HybridDictionary userStateToLifetime = 
        new HybridDictionary();

    private System.ComponentModel.Container components = null;

    /////////////////////////////////////////////////////////////
    #region Public events

    public event ProgressChangedEventHandler ProgressChanged;
    public event CalculatePrimeCompletedEventHandler CalculatePrimeCompleted;

    #endregion

    /////////////////////////////////////////////////////////////
    #region Construction and destruction

    public PrimeNumberCalculator(IContainer container)
    {   
        container.Add(this);
        InitializeComponent();

        InitializeDelegates();
    }

    public PrimeNumberCalculator()
    {   
        InitializeComponent();

        InitializeDelegates();
    }

    protected virtual void InitializeDelegates()
    {
        onProgressReportDelegate =
            new SendOrPostCallback(ReportProgress);
        onCompletedDelegate =
            new SendOrPostCallback(CalculateCompleted);
    }

    protected override void Dispose(bool disposing)
    {
        if (disposing)
        {
            if (components != null)
            {
                components.Dispose();
            }
        }
        base.Dispose(disposing);
    }

    #endregion // Construction and destruction

    /////////////////////////////////////////////////////////////
    ///
    #region Implementation

    // This method starts an asynchronous calculation. 
    // First, it checks the supplied task ID for uniqueness.
    // If taskId is unique, it creates a new WorkerEventHandler 
    // and calls its BeginInvoke method to start the calculation.
    public virtual void CalculatePrimeAsync(
        int numberToTest,
        object taskId)
    {
        // Create an AsyncOperation for taskId.
        AsyncOperation asyncOp =
            AsyncOperationManager.CreateOperation(taskId);

        // Multiple threads will access the task dictionary,
        // so it must be locked to serialize access.
        lock (userStateToLifetime.SyncRoot)
        {
            if (userStateToLifetime.Contains(taskId))
            {
                throw new ArgumentException(
                    "Task ID parameter must be unique", 
                    "taskId");
            }

            userStateToLifetime[taskId] = asyncOp;
        }

        // Start the asynchronous operation.
        WorkerEventHandler workerDelegate = new WorkerEventHandler(CalculateWorker);
        workerDelegate.BeginInvoke(
            numberToTest,
            asyncOp,
            null,
            null);
    }

    // Utility method for determining if a 
    // task has been canceled.
    private bool TaskCanceled(object taskId)
    {
        return( userStateToLifetime[taskId] == null );
    }

    // This method cancels a pending asynchronous operation.
    public void CancelAsync(object taskId)
    {
        AsyncOperation asyncOp = userStateToLifetime[taskId] as AsyncOperation;
        if (asyncOp != null)
        {   
            lock (userStateToLifetime.SyncRoot)
            {
                userStateToLifetime.Remove(taskId);
            }
        }
    }

    // This method performs the actual prime number computation.
    // It is executed on the worker thread.
    private void CalculateWorker(
        int numberToTest,
        AsyncOperation asyncOp)
    {
        bool isPrime = false;
        int firstDivisor = 1;
        Exception e = null;

        // Check that the task is still active.
        // The operation may have been canceled before
        // the thread was scheduled.
        if (!TaskCanceled(asyncOp.UserSuppliedState))
        {
            try
            {
                // Find all the prime numbers up to 
                // the square root of numberToTest.
                ArrayList primes = BuildPrimeNumberList(
                    numberToTest,
                    asyncOp);

                // Now we have a list of primes less than
                // numberToTest.
                isPrime = IsPrime(
                    primes,
                    numberToTest,
                    out firstDivisor);
            }
            catch (Exception ex)
            {
                e = ex;
            }
        }

        //CalculatePrimeState calcState = new CalculatePrimeState(
        //        numberToTest,
        //        firstDivisor,
        //        isPrime,
        //        e,
        //        TaskCanceled(asyncOp.UserSuppliedState),
        //        asyncOp);

        //this.CompletionMethod(calcState);

        this.CompletionMethod(
            numberToTest,
            firstDivisor,
            isPrime,
            e,
            TaskCanceled(asyncOp.UserSuppliedState),
            asyncOp);

        //completionMethodDelegate(calcState);
    }

    // This method computes the list of prime numbers used by the
    // IsPrime method.
    private ArrayList BuildPrimeNumberList(
        int numberToTest,
        AsyncOperation asyncOp)
    {
        ProgressChangedEventArgs e = null;
        ArrayList primes = new ArrayList();
        int firstDivisor;
        int n = 5;

        // Add the first prime numbers.
        primes.Add(2);
        primes.Add(3);

        // Do the work.
        while (n < numberToTest && 
               !TaskCanceled( asyncOp.UserSuppliedState ) )
        {
            if (IsPrime(primes, n, out firstDivisor))
            {
                // Report to the client that a prime was found.
                e = new CalculatePrimeProgressChangedEventArgs(
                    n,
                    (int)((float)n / (float)numberToTest * 100),
                    asyncOp.UserSuppliedState);

                asyncOp.Post(this.onProgressReportDelegate, e);

                primes.Add(n);

                // Yield the rest of this time slice.
                Thread.Sleep(0);
            }

            // Skip even numbers.
            n += 2;
        }

        return primes;
    }

    // This method tests n for primality against the list of 
    // prime numbers contained in the primes parameter.
    private bool IsPrime(
        ArrayList primes,
        int n,
        out int firstDivisor)
    {
        bool foundDivisor = false;
        bool exceedsSquareRoot = false;

        int i = 0;
        int divisor = 0;
        firstDivisor = 1;

        // Stop the search if:
        // there are no more primes in the list,
        // there is a divisor of n in the list, or
        // there is a prime that is larger than 
        // the square root of n.
        while (
            (i < primes.Count) &&
            !foundDivisor &&
            !exceedsSquareRoot)
        {
            // The divisor variable will be the smallest 
            // prime number not yet tried.
            divisor = (int)primes[i++];

            // Determine whether the divisor is greater
            // than the square root of n.
            if (divisor * divisor > n)
            {
                exceedsSquareRoot = true;
            }
            // Determine whether the divisor is a factor of n.
            else if (n % divisor == 0)
            {
                firstDivisor = divisor;
                foundDivisor = true;
            }
        }

        return !foundDivisor;
    }

    // This method is invoked via the AsyncOperation object,
    // so it is guaranteed to be executed on the correct thread.
    private void CalculateCompleted(object operationState)
    {
        CalculatePrimeCompletedEventArgs e =
            operationState as CalculatePrimeCompletedEventArgs;

        OnCalculatePrimeCompleted(e);
    }

    // This method is invoked via the AsyncOperation object,
    // so it is guaranteed to be executed on the correct thread.
    private void ReportProgress(object state)
    {
        ProgressChangedEventArgs e =
            state as ProgressChangedEventArgs;

        OnProgressChanged(e);
    }

    protected void OnCalculatePrimeCompleted(
        CalculatePrimeCompletedEventArgs e)
    {
        if (CalculatePrimeCompleted != null)
        {
            CalculatePrimeCompleted(this, e);
        }
    }

    protected void OnProgressChanged(ProgressChangedEventArgs e)
    {
        if (ProgressChanged != null)
        {
            ProgressChanged(e);
        }
    }

    // This is the method that the underlying, free-threaded 
    // asynchronous behavior will invoke.  This will happen on
    // an arbitrary thread.
    private void CompletionMethod( 
        int numberToTest,
        int firstDivisor, 
        bool isPrime,
        Exception exception, 
        bool canceled,
        AsyncOperation asyncOp )

    {
        // If the task was not previously canceled,
        // remove the task from the lifetime collection.
        if (!canceled)
        {
            lock (userStateToLifetime.SyncRoot)
            {
                userStateToLifetime.Remove(asyncOp.UserSuppliedState);
            }
        }

        // Package the results of the operation in a 
        // CalculatePrimeCompletedEventArgs.
        CalculatePrimeCompletedEventArgs e =
            new CalculatePrimeCompletedEventArgs(
            numberToTest,
            firstDivisor,
            isPrime,
            exception,
            canceled,
            asyncOp.UserSuppliedState);

        // End the task. The asyncOp object is responsible 
        // for marshaling the call.
        asyncOp.PostOperationCompleted(onCompletedDelegate, e);

        // Note that after the call to OperationCompleted, 
        // asyncOp is no longer usable, and any attempt to use it
        // will cause an exception to be thrown.
    }


    #endregion

    /////////////////////////////////////////////////////////////
    #region Component Designer generated code

    private void InitializeComponent()
    {
        components = new System.ComponentModel.Container();
    }

    #endregion

}

public class CalculatePrimeProgressChangedEventArgs :
        ProgressChangedEventArgs
{
    private int latestPrimeNumberValue = 1;

    public CalculatePrimeProgressChangedEventArgs(
        int latestPrime,
        int progressPercentage,
        object userToken) : base( progressPercentage, userToken )
    {
        this.latestPrimeNumberValue = latestPrime;
    }

    public int LatestPrimeNumber
    {
        get
        {
            return latestPrimeNumberValue;
        }
    }
}

public class CalculatePrimeCompletedEventArgs :
    AsyncCompletedEventArgs
{
    private int numberToTestValue = 0;
    private int firstDivisorValue = 1;
    private bool isPrimeValue;

    public CalculatePrimeCompletedEventArgs(
        int numberToTest,
        int firstDivisor,
        bool isPrime,
        Exception e,
        bool canceled,
        object state) : base(e, canceled, state)
    {
        this.numberToTestValue = numberToTest;
        this.firstDivisorValue = firstDivisor;
        this.isPrimeValue = isPrime;
    }

    public int NumberToTest
    {
        get
        {
            // Raise an exception if the operation failed or 
            // was canceled.
            RaiseExceptionIfNecessary();

            // If the operation was successful, return the 
            // property value.
            return numberToTestValue;
        }
    }

    public int FirstDivisor
    {
        get
        {
            // Raise an exception if the operation failed or 
            // was canceled.
            RaiseExceptionIfNecessary();

            // If the operation was successful, return the 
            // property value.
            return firstDivisorValue;
        }
    }

    public bool IsPrime
    {
        get
        {
            // Raise an exception if the operation failed or 
            // was canceled.
            RaiseExceptionIfNecessary();

            // If the operation was successful, return the 
            // property value.
            return isPrimeValue;
        }
    }
}


#endregion

import System.*;
import System.Collections.*;
import System.Collections.Specialized.*;
import System.ComponentModel.*;
import System.Data.*;
import System.Drawing.*;
import System.Threading.*;
import System.Windows.Forms.*;

Consulte também

Tarefas

Demonstra Passo a passo: Um componente que oferece suporte ao implementar o padrão assíncrono baseado em evento

Referência

AsyncOperation

AsyncOperationManager

WindowsFormsSynchronizationContext