.NET 中是否有类似于 Qt::QueuedConnection 的东西？答案

【问题标题】：Is there something analogous to Qt::QueuedConnection in .NET?.NET 中是否有类似于 Qt::QueuedConnection 的东西？
【发布时间】：2011-05-01 12:54:55
【问题描述】：

在 Qt 中，有一个很好的习惯用法是让每个对象都有associated with a thread，这样它的所有事件处理程序都会only run in that thread（当然，除非直接调用）。

在 C#/.NET 中是否有类似的东西？如果没有，您将如何开始自己编写？

例子：

// threaded.h
#include <QThread>
#include <QDebug>
#include <QtGlobal>

class ThreadedObject : public QObject {
    Q_OBJECT
public:
    ThreadedObject(const QString &name){
        Name = name;
        // the default QThread implementation is an empty event loop
        Thread = new QThread(this);
        moveToThread(Thread);
        Thread->start();
    }

public slots:
    void tick() {
        qDebug() << Name << "in thread" << (int)QThread::currentThreadId();
    }

private:
    QThread *Thread;
    QString Name;
};

和

// main.cpp
#include <QtCore/QCoreApplication>
#include <QTimer>
#include "threaded.h"


int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

    ThreadedObject *foo = new ThreadedObject("Foo");
    QTimer footimer;
    QObject::connect(&footimer, SIGNAL(timeout()), foo, SLOT(tick()));

    ThreadedObject *bar = new ThreadedObject("Bar");
    QTimer bartimer;
    QObject::connect(&bartimer, SIGNAL(timeout()), bar, SLOT(tick()));

    qDebug() << "Main thread is" << (int)QThread::currentThreadId();

    footimer.start(1300);
    bartimer.start(3240);

    return a.exec();
}

将输出：

Main thread is 3916 
"Foo" in thread 3824 
"Foo" in thread 3824 
"Bar" in thread 3920 
"Foo" in thread 3824 
...

【问题讨论】：

标签： c# .net multithreading qt thread-safety

【解决方案1】：

WPF 调度程序！

using System;
using System.Windows.Threading;
using System.Threading;

namespace dispatchertest
{
    public class Dispatched : DispatcherObject
    {
        readonly object Lock = new object();
        readonly string _name;
        public string Name { get { return _name; } }

        public Dispatched(string name) {
            this._name = name;
        }

        public void tick(object sender, EventArgs e) {
            lock ( Lock ) {
                Console.WriteLine("{0} in thread {1}", Name, Thread.CurrentThread.ManagedThreadId);
            }
        }
    }

    class Program
    {
        static void Main(string[] args) {

            var timer = new DispatcherTimer(DispatcherPriority.Send, Dispatcher.CurrentDispatcher);

            Thread thread1 = new Thread(() => {
                var d2 = Dispatcher.CurrentDispatcher;
                var foo = new Dispatched("Foo");


                var timer1 = new DispatcherTimer(DispatcherPriority.Send, Dispatcher.CurrentDispatcher);
                timer1.Interval = new TimeSpan(0,0,0,0, milliseconds: 809);
                timer1.Tick += foo.tick;


                timer1.Start();
                Dispatcher.Run();
            });

            var bar = new Dispatched("Bar");
            timer.Tick += bar.tick;

            thread1.Start();

            timer.Interval = new TimeSpan(0,0,0,0, milliseconds: 1234);
            timer.Start();
            Dispatcher.Run();
        }
    }
}

输出：

Foo in thread 10
Bar in thread 9
Foo in thread 10
Foo in thread 10
Bar in thread 9
Foo in thread 10
Bar in thread 9
Foo in thread 10
Foo in thread 10
Bar in thread 9
Foo in thread 10
Bar in thread 9
Foo in thread 10
Foo in thread 10

【讨论】：

仅供参考 - WPF 的调度程序是一种特定于 WPF 的 SynchronizationContext 形式...

【解决方案2】：

.NET 中与此最接近的类比可能是SynchronizationContext。

例如，Task Parallel Library 使用它来将 continations 编组回 UI 线程。

但是，没有适用于任何线程的内置实现。在 .NET 4 中使用BlockingCollection<T> 编写一个相当容易，但它不包含在框架中。它也有些不同，因为它不会自动为您将事件编组回该线程 - 它更像是提供此类操作所需功能的构建块。

【讨论】：