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Postupy: Určení plánovače úloh v bloku toku dat

  • Článek

Tento dokument ukazuje, jak přidružit konkrétní plánovač úloh při použití toku dat v aplikaci. Příklad používá System.Threading.Tasks.ConcurrentExclusiveSchedulerPair třídu v aplikaci model Windows Forms k zobrazení, kdy jsou úkoly čtenáře aktivní a kdy je úkol zapisovače aktivní. Používá také metodu TaskScheduler.FromCurrentSynchronizationContext k povolení spuštění bloku toku dat ve vlákně uživatelského rozhraní.

Poznámka:

Knihovna toku dat TPL ( System.Threading.Tasks.Dataflow obor názvů) není distribuována s .NET. Pokud chcete nainstalovat System.Threading.Tasks.Dataflow obor názvů v sadě Visual Studio, otevřete projekt, v nabídce Projekt zvolte Spravovat balíčky NuGet a vyhledejte System.Threading.Tasks.Dataflow balíček online. Pokud ho chcete nainstalovat pomocí rozhraní příkazového řádku .NET Core, spusťte dotnet add package System.Threading.Tasks.Dataflow.

Vytvoření aplikace model Windows Forms

  1. Vytvořte projekt aplikace Visual C# nebo Visual Basic model Windows Forms. V následujících krocích má projekt název WriterReadersWinForms.

  2. V návrháři formulářů pro hlavní formulář Form1.cs (Form1.vb pro Visual Basic) přidejte čtyři CheckBox ovládací prvky. Text Nastavte vlastnost Čtenář 1 pro checkBox1, Čtenář 2 pro checkBox2, Čtenář 3 pro checkBox3a Writer pro checkBox4. Enabled Nastavte vlastnost pro každý ovládací prvek na Falsehodnotu .

  3. Timer Přidejte do formuláře ovládací prvek. Nastavte vlastnost Interval na 2500.

Přidání funkce toku dat

Tato část popisuje, jak vytvořit bloky toku dat, které se účastní aplikace, a jak je přidružit k plánovači úloh.

Přidání funkce toku dat do aplikace

  1. V projektu přidejte odkaz na System.Threading.Tasks.Dataflow.dll.

  2. Ujistěte se, že Form1.cs (Form1.vb pro Visual Basic) obsahuje následující using direktivy (Imports v jazyce Visual Basic).

    using System;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using System.Threading.Tasks.Dataflow;
using System.Windows.Forms;

    Imports System.Threading
Imports System.Threading.Tasks
Imports System.Threading.Tasks.Dataflow

  3. BroadcastBlock<T> Přidejte do Form1 třídy datový člen.

    // Broadcasts values to an ActionBlock<int> object that is associated
// with each check box.
BroadcastBlock<int> broadcaster = new BroadcastBlock<int>(null);

    ' Broadcasts values to an ActionBlock<int> object that is associated
' with each check box.
Private broadcaster As New BroadcastBlock(Of Integer)(Nothing)

  4. V konstruktoru Form1 za voláním InitializeComponentvytvořte ActionBlock<TInput> objekt, který přepíná stav CheckBox objektů.

    // Create an ActionBlock<CheckBox> object that toggles the state
// of CheckBox objects.
// Specifying the current synchronization context enables the
// action to run on the user-interface thread.
var toggleCheckBox = new ActionBlock<CheckBox>(checkBox =>
{
   checkBox.Checked = !checkBox.Checked;
},
new ExecutionDataflowBlockOptions
{
   TaskScheduler = TaskScheduler.FromCurrentSynchronizationContext()
});

    ' Create an ActionBlock<CheckBox> object that toggles the state
' of CheckBox objects.
' Specifying the current synchronization context enables the 
' action to run on the user-interface thread.
Dim toggleCheckBox = New ActionBlock(Of CheckBox)(Sub(checkBox) checkBox.Checked = Not checkBox.Checked, New ExecutionDataflowBlockOptions With {.TaskScheduler = TaskScheduler.FromCurrentSynchronizationContext()})

  5. V konstruktoru Form1 vytvořte ConcurrentExclusiveSchedulerPair objekt a čtyři ActionBlock<TInput> objekty, jeden ActionBlock<TInput> objekt pro každý CheckBox objekt. U každého ActionBlock<TInput> objektu ExecutionDataflowBlockOptions zadejte objekt, který má TaskScheduler vlastnost nastavenou ConcurrentScheduler na vlastnost pro čtenáře, a ExclusiveScheduler vlastnost pro zapisovač.

    // Create a ConcurrentExclusiveSchedulerPair object.
// Readers will run on the concurrent part of the scheduler pair.
// The writer will run on the exclusive part of the scheduler pair.
var taskSchedulerPair = new ConcurrentExclusiveSchedulerPair();

// Create an ActionBlock<int> object for each reader CheckBox object.
// Each ActionBlock<int> object represents an action that can read
// from a resource in parallel to other readers.
// Specifying the concurrent part of the scheduler pair enables the
// reader to run in parallel to other actions that are managed by
// that scheduler.
var readerActions =
   from checkBox in new CheckBox[] {checkBox1, checkBox2, checkBox3}
   select new ActionBlock<int>(milliseconds =>
   {
      // Toggle the check box to the checked state.
      toggleCheckBox.Post(checkBox);

      // Perform the read action. For demonstration, suspend the current
      // thread to simulate a lengthy read operation.
      Thread.Sleep(milliseconds);

      // Toggle the check box to the unchecked state.
      toggleCheckBox.Post(checkBox);
   },
   new ExecutionDataflowBlockOptions
   {
      TaskScheduler = taskSchedulerPair.ConcurrentScheduler
   });

// Create an ActionBlock<int> object for the writer CheckBox object.
// This ActionBlock<int> object represents an action that writes to
// a resource, but cannot run in parallel to readers.
// Specifying the exclusive part of the scheduler pair enables the
// writer to run in exclusively with respect to other actions that are
// managed by the scheduler pair.
var writerAction = new ActionBlock<int>(milliseconds =>
{
   // Toggle the check box to the checked state.
   toggleCheckBox.Post(checkBox4);

   // Perform the write action. For demonstration, suspend the current
   // thread to simulate a lengthy write operation.
   Thread.Sleep(milliseconds);

   // Toggle the check box to the unchecked state.
   toggleCheckBox.Post(checkBox4);
},
new ExecutionDataflowBlockOptions
{
   TaskScheduler = taskSchedulerPair.ExclusiveScheduler
});

// Link the broadcaster to each reader and writer block.
// The BroadcastBlock<T> class propagates values that it
// receives to all connected targets.
foreach (var readerAction in readerActions)
{
   broadcaster.LinkTo(readerAction);
}
broadcaster.LinkTo(writerAction);

    ' Create a ConcurrentExclusiveSchedulerPair object.
' Readers will run on the concurrent part of the scheduler pair.
' The writer will run on the exclusive part of the scheduler pair.
Dim taskSchedulerPair = New ConcurrentExclusiveSchedulerPair()

' Create an ActionBlock<int> object for each reader CheckBox object.
' Each ActionBlock<int> object represents an action that can read 
' from a resource in parallel to other readers.
' Specifying the concurrent part of the scheduler pair enables the 
' reader to run in parallel to other actions that are managed by 
' that scheduler.
Dim readerActions = From checkBox In New CheckBox() {checkBox1, checkBox2, checkBox3} _
                    Select New ActionBlock(Of Integer)(Sub(milliseconds)
                                           ' Toggle the check box to the checked state.
                                           ' Perform the read action. For demonstration, suspend the current
                                           ' thread to simulate a lengthy read operation.
                                           ' Toggle the check box to the unchecked state.
                                           toggleCheckBox.Post(checkBox)
                                                           Thread.Sleep(milliseconds)
                                                           toggleCheckBox.Post(checkBox)
                                                       End Sub, New ExecutionDataflowBlockOptions With {.TaskScheduler = taskSchedulerPair.ConcurrentScheduler})

' Create an ActionBlock<int> object for the writer CheckBox object.
' This ActionBlock<int> object represents an action that writes to 
' a resource, but cannot run in parallel to readers.
' Specifying the exclusive part of the scheduler pair enables the 
' writer to run in exclusively with respect to other actions that are 
' managed by the scheduler pair.
Dim writerAction = New ActionBlock(Of Integer)(Sub(milliseconds)
                                                   ' Toggle the check box to the checked state.
                                                   ' Perform the write action. For demonstration, suspend the current
                                                   ' thread to simulate a lengthy write operation.
                                                   ' Toggle the check box to the unchecked state.
                                                   toggleCheckBox.Post(checkBox4)
                                                   Thread.Sleep(milliseconds)
                                                   toggleCheckBox.Post(checkBox4)
                                               End Sub, New ExecutionDataflowBlockOptions With {.TaskScheduler = taskSchedulerPair.ExclusiveScheduler})

' Link the broadcaster to each reader and writer block.
' The BroadcastBlock<T> class propagates values that it 
' receives to all connected targets.
For Each readerAction In readerActions
    broadcaster.LinkTo(readerAction)
Next readerAction
broadcaster.LinkTo(writerAction)

  6. V konstruktoru Form1Timer spusťte objekt.

    // Start the timer.
timer1.Start();

    ' Start the timer.
timer1.Start()

  7. V návrháři formulářů pro hlavní formulář vytvořte obslužnou rutinu události pro Tick časovač.

  8. Tick Implementujte událost časovače.

    // Event handler for the timer.
private void timer1_Tick(object sender, EventArgs e)
{
   // Post a value to the broadcaster. The broadcaster
   // sends this message to each target.
   broadcaster.Post(1000);
}

    ' Event handler for the timer.
Private Sub timer1_Tick(ByVal sender As Object, ByVal e As EventArgs) Handles timer1.Tick
    ' Post a value to the broadcaster. The broadcaster
    ' sends this message to each target. 
    broadcaster.Post(1000)
End Sub

Vzhledem k tomu, že toggleCheckBox blok toku dat funguje na uživatelském rozhraní, je důležité, aby tato akce probíhala ve vlákně uživatelského rozhraní. Chcete-li toho dosáhnout, během vytváření tohoto objektu poskytuje ExecutionDataflowBlockOptions objekt, který má vlastnost nastavena TaskScheduler na TaskScheduler.FromCurrentSynchronizationContext. Metoda FromCurrentSynchronizationContext vytvoří TaskScheduler objekt, který provádí práci s aktuálním kontextem synchronizace. Vzhledem k tomu, že Form1 se konstruktor volá z vlákna uživatelského rozhraní, akce pro toggleCheckBox blok toku dat také běží na vlákně uživatelského rozhraní.

Tento příklad také používá ConcurrentExclusiveSchedulerPair třídu k tomu, aby některé bloky toku dat fungovaly souběžně, a další blok toku dat, který funguje výhradně s ohledem na všechny ostatní bloky toku dat, které běží na stejném ConcurrentExclusiveSchedulerPair objektu. Tato technika je užitečná, když několik toků dat sdílí prostředek a některé vyžadují výhradní přístup k tomuto prostředku, protože eliminuje požadavek na ruční synchronizaci přístupu k tomuto prostředku. Odstranění ruční synchronizace může zefektivnit kód.

Příklad

Následující příklad ukazuje úplný kód pro Form1.cs (Form1.vb pro Visual Basic).

using System;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using System.Threading.Tasks.Dataflow;
using System.Windows.Forms;

namespace WriterReadersWinForms
{
   public partial class Form1 : Form
   {
      // Broadcasts values to an ActionBlock<int> object that is associated
      // with each check box.
      BroadcastBlock<int> broadcaster = new BroadcastBlock<int>(null);

      public Form1()
      {
         InitializeComponent();

         // Create an ActionBlock<CheckBox> object that toggles the state
         // of CheckBox objects.
         // Specifying the current synchronization context enables the
         // action to run on the user-interface thread.
         var toggleCheckBox = new ActionBlock<CheckBox>(checkBox =>
         {
            checkBox.Checked = !checkBox.Checked;
         },
         new ExecutionDataflowBlockOptions
         {
            TaskScheduler = TaskScheduler.FromCurrentSynchronizationContext()
         });

         // Create a ConcurrentExclusiveSchedulerPair object.
         // Readers will run on the concurrent part of the scheduler pair.
         // The writer will run on the exclusive part of the scheduler pair.
         var taskSchedulerPair = new ConcurrentExclusiveSchedulerPair();

         // Create an ActionBlock<int> object for each reader CheckBox object.
         // Each ActionBlock<int> object represents an action that can read
         // from a resource in parallel to other readers.
         // Specifying the concurrent part of the scheduler pair enables the
         // reader to run in parallel to other actions that are managed by
         // that scheduler.
         var readerActions =
            from checkBox in new CheckBox[] {checkBox1, checkBox2, checkBox3}
            select new ActionBlock<int>(milliseconds =>
            {
               // Toggle the check box to the checked state.
               toggleCheckBox.Post(checkBox);

               // Perform the read action. For demonstration, suspend the current
               // thread to simulate a lengthy read operation.
               Thread.Sleep(milliseconds);

               // Toggle the check box to the unchecked state.
               toggleCheckBox.Post(checkBox);
            },
            new ExecutionDataflowBlockOptions
            {
               TaskScheduler = taskSchedulerPair.ConcurrentScheduler
            });

         // Create an ActionBlock<int> object for the writer CheckBox object.
         // This ActionBlock<int> object represents an action that writes to
         // a resource, but cannot run in parallel to readers.
         // Specifying the exclusive part of the scheduler pair enables the
         // writer to run in exclusively with respect to other actions that are
         // managed by the scheduler pair.
         var writerAction = new ActionBlock<int>(milliseconds =>
         {
            // Toggle the check box to the checked state.
            toggleCheckBox.Post(checkBox4);

            // Perform the write action. For demonstration, suspend the current
            // thread to simulate a lengthy write operation.
            Thread.Sleep(milliseconds);

            // Toggle the check box to the unchecked state.
            toggleCheckBox.Post(checkBox4);
         },
         new ExecutionDataflowBlockOptions
         {
            TaskScheduler = taskSchedulerPair.ExclusiveScheduler
         });

         // Link the broadcaster to each reader and writer block.
         // The BroadcastBlock<T> class propagates values that it
         // receives to all connected targets.
         foreach (var readerAction in readerActions)
         {
            broadcaster.LinkTo(readerAction);
         }
         broadcaster.LinkTo(writerAction);

         // Start the timer.
         timer1.Start();
      }

      // Event handler for the timer.
      private void timer1_Tick(object sender, EventArgs e)
      {
         // Post a value to the broadcaster. The broadcaster
         // sends this message to each target.
         broadcaster.Post(1000);
      }
   }
}

Imports System.Threading
Imports System.Threading.Tasks
Imports System.Threading.Tasks.Dataflow


Namespace WriterReadersWinForms
    Partial Public Class Form1
        Inherits Form
        ' Broadcasts values to an ActionBlock<int> object that is associated
        ' with each check box.
        Private broadcaster As New BroadcastBlock(Of Integer)(Nothing)

        Public Sub New()
            InitializeComponent()

            ' Create an ActionBlock<CheckBox> object that toggles the state
            ' of CheckBox objects.
            ' Specifying the current synchronization context enables the 
            ' action to run on the user-interface thread.
            Dim toggleCheckBox = New ActionBlock(Of CheckBox)(Sub(checkBox) checkBox.Checked = Not checkBox.Checked, New ExecutionDataflowBlockOptions With {.TaskScheduler = TaskScheduler.FromCurrentSynchronizationContext()})

            ' Create a ConcurrentExclusiveSchedulerPair object.
            ' Readers will run on the concurrent part of the scheduler pair.
            ' The writer will run on the exclusive part of the scheduler pair.
            Dim taskSchedulerPair = New ConcurrentExclusiveSchedulerPair()

            ' Create an ActionBlock<int> object for each reader CheckBox object.
            ' Each ActionBlock<int> object represents an action that can read 
            ' from a resource in parallel to other readers.
            ' Specifying the concurrent part of the scheduler pair enables the 
            ' reader to run in parallel to other actions that are managed by 
            ' that scheduler.
            Dim readerActions = From checkBox In New CheckBox() {checkBox1, checkBox2, checkBox3} _
                                Select New ActionBlock(Of Integer)(Sub(milliseconds)
                                                       ' Toggle the check box to the checked state.
                                                       ' Perform the read action. For demonstration, suspend the current
                                                       ' thread to simulate a lengthy read operation.
                                                       ' Toggle the check box to the unchecked state.
                                                       toggleCheckBox.Post(checkBox)
                                                                       Thread.Sleep(milliseconds)
                                                                       toggleCheckBox.Post(checkBox)
                                                                   End Sub, New ExecutionDataflowBlockOptions With {.TaskScheduler = taskSchedulerPair.ConcurrentScheduler})

            ' Create an ActionBlock<int> object for the writer CheckBox object.
            ' This ActionBlock<int> object represents an action that writes to 
            ' a resource, but cannot run in parallel to readers.
            ' Specifying the exclusive part of the scheduler pair enables the 
            ' writer to run in exclusively with respect to other actions that are 
            ' managed by the scheduler pair.
            Dim writerAction = New ActionBlock(Of Integer)(Sub(milliseconds)
                                                               ' Toggle the check box to the checked state.
                                                               ' Perform the write action. For demonstration, suspend the current
                                                               ' thread to simulate a lengthy write operation.
                                                               ' Toggle the check box to the unchecked state.
                                                               toggleCheckBox.Post(checkBox4)
                                                               Thread.Sleep(milliseconds)
                                                               toggleCheckBox.Post(checkBox4)
                                                           End Sub, New ExecutionDataflowBlockOptions With {.TaskScheduler = taskSchedulerPair.ExclusiveScheduler})

            ' Link the broadcaster to each reader and writer block.
            ' The BroadcastBlock<T> class propagates values that it 
            ' receives to all connected targets.
            For Each readerAction In readerActions
                broadcaster.LinkTo(readerAction)
            Next readerAction
            broadcaster.LinkTo(writerAction)

            ' Start the timer.
            timer1.Start()
        End Sub

        ' Event handler for the timer.
        Private Sub timer1_Tick(ByVal sender As Object, ByVal e As EventArgs) Handles timer1.Tick
            ' Post a value to the broadcaster. The broadcaster
            ' sends this message to each target. 
            broadcaster.Post(1000)
        End Sub
    End Class
End Namespace

Viz také