Question

我有一个IEnumerable序列，其中包含一些阻塞网络操作（在下面的示例代码中替换为一些简单的产量）。我正在使用Reactive Extensions将来自网络的数据流转换为可观察的序列。

我正在寻找一种方法来将异常编组到主线程中，以便未处理的异常不会导致我的应用程序终止。我不能在IEnumerable线程上放置try / catch块，因为编译器不允许在try / catch语句中使用yield return语句。

using System;
using System.Collections.Generic;
using System.Concurrency;
using System.Linq;
using System.Text;
using System.Threading;

namespace ConsoleApplication7
{
    class Program
    {
        static void Main(string[] args)
        {
            try
            {
                Console.WriteLine("Main thread: " + System.Threading.Thread.CurrentThread.ManagedThreadId);
                var observable = TestEnumerable().ToObservable(Scheduler.NewThread); //Needs to be on a new thread because it contains long-running blocking operations

                // Use subject because we need many subscriptions to a single data source
                var subject = new Subject<int>();

                subject.Subscribe(x => Console.WriteLine("Subscriber1: " + x + " on thread: " + System.Threading.Thread.CurrentThread.ManagedThreadId),
                    x => Console.WriteLine("Subscriber1 ERROR: " + x+ " on thread: " + System.Threading.Thread.CurrentThread.ManagedThreadId),
                    () => Console.WriteLine("Subscriber1 Finished"+ " on thread: " + System.Threading.Thread.CurrentThread.ManagedThreadId));
                subject.Subscribe(x => Console.WriteLine("Subscriber2: " + x + " on thread: " + System.Threading.Thread.CurrentThread.ManagedThreadId),
                    x => Console.WriteLine("Subscriber2 ERROR: " + x+ " on thread: " + System.Threading.Thread.CurrentThread.ManagedThreadId),
                    () => Console.WriteLine("Subscriber2 Finished"+ " on thread: " + System.Threading.Thread.CurrentThread.ManagedThreadId));

                Console.WriteLine("Press key to start receiving data");
                Console.ReadKey();
                var sub = observable.Subscribe(subject);

                Console.WriteLine("Press key to exit");
                Console.ReadKey();
                sub.Dispose();
            }
            catch (Exception ex)
            {
                Console.WriteLine("Caught exception on main thread");
            }

        }

        public static IEnumerable<int> TestEnumerable()
        {
            while (true)
            {
                yield return 1;
                Thread.Sleep(200);
                yield return 2;
                Thread.Sleep(200);
                yield return 3;
                Thread.Sleep(200);
                throw new InvalidOperationException();
            }
        }
    }
}

Answer 1

解决方案取决于您是否可以使用Dispatcher / SynchronisationContext。在这种情况下，最好使用一个。

解决方案1：Dispatcher / SynchronisationContext可用

（即使用WPF，Windows窗体或自定义Dispatcher循环）

您可以使用ObserveOn + Catch将错误移回Dispatcher线程。我已经看到在WPF应用程序中使用它并且它运行良好。

您如何移动IScheduler / DispatcherScheduler取决于您（我们使用IoC）

public static IObservable<T> CatchOn<T>(this IObservable<T> source, 
    IScheduler scheduler)
{
    return source.Catch<T,Exception>(ex => 
        Observable.Throw<T>(ex).ObserveOn(scheduler));
}

// We didn't use it, but this overload could useful if the dispatcher is 
// known at the time of execution, since it's an optimised path
public static IObservable<T> CatchOn<T>(this IObservable<T> source, 
    DispatcherScheduler scheduler)
{
    return source.Catch<T,Exception>(ex => 
        Observable.Throw<T>(ex).ObserveOn(scheduler));
}

解决方案2：没有可用的调度程序

不使用Console.ReadKey()，而是使用ManualResetEvent并等待它，然后抛出可变错误：

        static void Main(string[] args)
        {
            try
            {
                Console.WriteLine("Main thread: " + System.Threading.Thread.CurrentThread.ManagedThreadId);
                var observable = TestEnumerable().ToObservable(Scheduler.NewThread); //Needs to be on a new thread because it contains long-running blocking operations

                // Use subject because we need many subscriptions to a single data source
                var subject = new Subject<int>();

                Exception exception = null;
                ManualResetEvent mre = new ManualResetEvent(false);

                using(subject.Subscribe(
                    x => Console.WriteLine(x),
                    ex => { exception = ex; mre.Set(); },
                    () => Console.WriteLine("Subscriber2 Finished")))

                using(subject.Subscribe(
                    x => Console.WriteLine(x),
                    ex => { exception = ex; mre.Set(); },
                    () => Console.WriteLine("Subscriber2 Finished")))

                using (observable.Subscribe(subject))
                {
                    mre.WaitOne();
                }

                if (exception != null)
                    throw exception;
            }
            catch (Exception ex)
            {
                Console.WriteLine("Caught exception on main thread");
            }

        }

跨线程编组异常（Reactive Extensions）

1 个答案: