如何在asp.net C# 4.0中调用异步方法？

Question

我知道在.NET 4.5中有"await"和"async"关键字，可以轻松调用异步方法。我正在学习如何在C# 4.0中进行异步调用。我想要的一个示例是在数据绑定datagrid时进行异步调用。

如果您能提供一些链接，我将不胜感激。

- Randel Ramirez

Answer 1

建议您考虑使用Tasks，这在.Net 4中可用，可以帮助您。一个简单的示例可能是这样的：

public void MainFlow()
{
   Task taskWork = Task.Factory.StartNew(new Action(DoWork));
   //Do other work
   //Then wait for thread finish
   taskWork.Wait();
}


private void DoWork()
{
   //Do work
}

了解更多，请点击这里

- Justin Harvey

---

Task.Run在.Net 4.0中不存在。 - JPProgrammer

使用 Task.Factory.StartNew 适用于 .Net 4。 - Justin Harvey

Answer 2

我们创建了一些工具类来执行异步操作。

这些方法的真正作用是：异步执行操作，然后根据同步上下文发布完成的执行。

我们将其作为TPL的包装器，以便在调用长时间运行的操作时轻松地在WPF中使用。此类还具有可以取消而不仅仅是放弃的操作类似物。

public static class AsyncExecutor
    {
        public static CancellationTokenSource ExecuteBlockingOperation(Action action, Action completition, Action<AggregateException> onException)
        {
            if (action == null)
                throw new ArgumentNullException("action");

            if (completition == null)
                throw new ArgumentNullException("completition");

            var cts = new CancellationTokenSource();
            var token = cts.Token;

            var scheduler = TaskScheduler.FromCurrentSynchronizationContext();

            var task = new Task(action, TaskCreationOptions.LongRunning);
            task.ContinueWith(asyncPartTask => onException(asyncPartTask.Exception), CancellationToken.None, TaskContinuationOptions.OnlyOnFaulted, scheduler);
            task.ContinueWith(asyncPart =>
                                  {
                                      if (!token.IsCancellationRequested)
                                          completition();
                                  },
                              CancellationToken.None, TaskContinuationOptions.OnlyOnRanToCompletion, scheduler);
            task.Start();

            return cts;

        }

        public static CancellationTokenSource ExecuteBlockingOperation<TIn>(Action<TIn> action, TIn parameter, Action<TIn> completition, Action<AggregateException, TIn> onException)
        {
            if (action == null)
                throw new ArgumentNullException("action");

            if (completition == null)
                throw new ArgumentNullException("completition");

            var cts = new CancellationTokenSource();
            var token = cts.Token;

            var scheduler = TaskScheduler.FromCurrentSynchronizationContext();

            var task = new Task(() => action(parameter), TaskCreationOptions.LongRunning);
            task.ContinueWith(asyncPartTask => onException(asyncPartTask.Exception, parameter), CancellationToken.None, TaskContinuationOptions.OnlyOnFaulted, scheduler);
            task.ContinueWith(asyncPart =>
                                  {
                                      if (!token.IsCancellationRequested)
                                          completition(parameter);
                                  },
                              CancellationToken.None, TaskContinuationOptions.OnlyOnRanToCompletion, scheduler);
            task.Start();

            return cts;

        }

        public static CancellationTokenSource ExecuteBlockingOperation<TOut>(Func<TOut> func, Action<TOut> completition, Action<AggregateException> onException)
        {
            if (func == null)
                throw new ArgumentNullException("func");

            if (completition == null)
                throw new ArgumentNullException("completition");

            var cts = new CancellationTokenSource();
            var token = cts.Token;

            var scheduler = TaskScheduler.FromCurrentSynchronizationContext();

            var task = new Task<TOut>(func, TaskCreationOptions.LongRunning);
            task.ContinueWith(asyncPartTask => onException(asyncPartTask.Exception), CancellationToken.None, TaskContinuationOptions.OnlyOnFaulted, scheduler);
            task.ContinueWith(asyncPart =>
                                  {
                                      if (!token.IsCancellationRequested)
                                          completition(asyncPart.Result);
                                  },
                              CancellationToken.None, TaskContinuationOptions.OnlyOnRanToCompletion, scheduler);
            task.Start();

            return cts;

        }

        public static CancellationTokenSource ExecuteBlockingOperation<TIn, TOut>(Func<TIn, TOut> func, TIn parameter, Action<TOut, TIn> completition, Action<AggregateException, TIn> onException)
        {
            if (func == null)
                throw new ArgumentNullException("func");

            if (completition == null)
                throw new ArgumentNullException("completition");

            var cts = new CancellationTokenSource();
            var token = cts.Token;

            var scheduler = TaskScheduler.FromCurrentSynchronizationContext();

            var task = new Task<TOut>(() => func(parameter), TaskCreationOptions.LongRunning);
            task.ContinueWith(asyncPartTask => onException(asyncPartTask.Exception, parameter), CancellationToken.None, TaskContinuationOptions.OnlyOnFaulted, scheduler);
            task.ContinueWith(asyncPart =>
            {
                if (!token.IsCancellationRequested)
                    completition(asyncPart.Result, parameter);
            },
                              CancellationToken.None, TaskContinuationOptions.OnlyOnRanToCompletion, scheduler);
            task.Start();

            return cts;
        }

        public static CancellationTokenSource ExecuteBlockingOperation<TIn, TOut>(Func<TIn, TOut> func, TIn parameter, Action<TOut> completition, Action<AggregateException, TIn> onException)
        {
            if (func == null)
                throw new ArgumentNullException("func");

            if (completition == null)
                throw new ArgumentNullException("completition");

            var cts = new CancellationTokenSource();
            var token = cts.Token;

            var scheduler = TaskScheduler.FromCurrentSynchronizationContext();

            var task = new Task<TOut>(() => func(parameter), TaskCreationOptions.LongRunning);
            task.ContinueWith(asyncPartTask => onException(asyncPartTask.Exception, parameter), CancellationToken.None, TaskContinuationOptions.OnlyOnFaulted, scheduler);
            task.ContinueWith(asyncPart =>
            {
                if (!token.IsCancellationRequested)
                    completition(asyncPart.Result);
            },
                              CancellationToken.None, TaskContinuationOptions.OnlyOnRanToCompletion, scheduler);
            task.Start();

            return cts;
        }

        public static CancellationTokenSource ExecuteBlockingOperation<TIn, TOut>(Func<TIn, TOut> func, TIn parameter, Action<TIn> completition, Action<AggregateException, TIn> onException)
        {
            if (func == null)
                throw new ArgumentNullException("func");

            if (completition == null)
                throw new ArgumentNullException("completition");

            var cts = new CancellationTokenSource();
            var token = cts.Token;

            var scheduler = TaskScheduler.FromCurrentSynchronizationContext();

            var task = new Task<TOut>(() => func(parameter), TaskCreationOptions.LongRunning);
            task.ContinueWith(asyncPartTask => onException(asyncPartTask.Exception, parameter), CancellationToken.None, TaskContinuationOptions.OnlyOnFaulted, scheduler);
            task.ContinueWith(asyncPart =>
            {
                if (!token.IsCancellationRequested)
                    completition(parameter);
            },
                              CancellationToken.None, TaskContinuationOptions.OnlyOnRanToCompletion, scheduler);
            task.Start();

            return cts;
        }

        public static CancellationTokenSource ExecuteBlockingOperation<TIn, TOut>(Func<TIn, TOut> func, TIn parameter, Action completition, Action<AggregateException, TIn> onException)
        {
            if (func == null)
                throw new ArgumentNullException("func");

            if (completition == null)
                throw new ArgumentNullException("completition");

            var cts = new CancellationTokenSource();
            var token = cts.Token;

            var scheduler = TaskScheduler.FromCurrentSynchronizationContext();

            var task = new Task<TOut>(() => func(parameter), TaskCreationOptions.LongRunning);
            task.ContinueWith(asyncPartTask => onException(asyncPartTask.Exception, parameter), CancellationToken.None, TaskContinuationOptions.OnlyOnFaulted, scheduler);
            task.ContinueWith(asyncPart =>
            {
                if (!token.IsCancellationRequested)
                    completition();
            },
                              CancellationToken.None, TaskContinuationOptions.OnlyOnRanToCompletion, scheduler);
            task.Start();

            return cts;
        }

        public static CancellationTokenSource ExecuteBlockingOperation<TIn, TOut>(Func<TIn, TOut> func, TIn parameter, Action<TIn> completition, Action<AggregateException> onException)
        {
            if (func == null)
                throw new ArgumentNullException("func");

            if (completition == null)
                throw new ArgumentNullException("completition");

            var cts = new CancellationTokenSource();
            var token = cts.Token;

            var scheduler = TaskScheduler.FromCurrentSynchronizationContext();

            var task = new Task<TOut>(() => func(parameter), TaskCreationOptions.LongRunning);
            task.ContinueWith(asyncPartTask => onException(asyncPartTask.Exception), CancellationToken.None, TaskContinuationOptions.OnlyOnFaulted, scheduler);
            task.ContinueWith(asyncPart =>
            {
                if (!token.IsCancellationRequested)
                    completition(parameter);
            },
                              CancellationToken.None, TaskContinuationOptions.OnlyOnRanToCompletion, scheduler);
            task.Start();

            return cts;
        }

        public static CancellationTokenSource ExecuteBlockingOperation<TIn, TOut>(Func<TIn, TOut> func, TIn parameter, Action<TOut, TIn> completition, Action<AggregateException> onException)
        {
            if (func == null)
                throw new ArgumentNullException("func");

            if (completition == null)
                throw new ArgumentNullException("completition");

            var cts = new CancellationTokenSource();
            var token = cts.Token;

            var scheduler = TaskScheduler.FromCurrentSynchronizationContext();

            var task = new Task<TOut>(() => func(parameter), TaskCreationOptions.LongRunning);
            task.ContinueWith(asyncPartTask => onException(asyncPartTask.Exception), CancellationToken.None, TaskContinuationOptions.OnlyOnFaulted, scheduler);
            task.ContinueWith(asyncPart =>
            {
                if (!token.IsCancellationRequested)
                    completition(asyncPart.Result, parameter);
            },
                              CancellationToken.None, TaskContinuationOptions.OnlyOnRanToCompletion, scheduler);
            task.Start();

            return cts;
        }

        public static CancellationTokenSource ExecuteBlockingOperation<TIn, TOut>(Func<TIn, TOut> func, TIn parameter, Action<TOut> completition, Action<AggregateException> onException)
        {
            if (func == null)
                throw new ArgumentNullException("func");

            if (completition == null)
                throw new ArgumentNullException("completition");

            var cts = new CancellationTokenSource();
            var token = cts.Token;

            var scheduler = TaskScheduler.FromCurrentSynchronizationContext();

            var task = new Task<TOut>(() => func(parameter), TaskCreationOptions.LongRunning);
            task.ContinueWith(asyncPartTask => onException(asyncPartTask.Exception), CancellationToken.None, TaskContinuationOptions.OnlyOnFaulted, scheduler);
            task.ContinueWith(asyncPart =>
            {
                if (!token.IsCancellationRequested)
                    completition(asyncPart.Result);
            },
                              CancellationToken.None, TaskContinuationOptions.OnlyOnRanToCompletion, scheduler);
            task.Start();

            return cts;
        }

        public static CancellationTokenSource ExecuteBlockingOperation<TIn, TOut>(Func<TIn, TOut> func, TIn parameter, Action completition, Action<AggregateException> onException)
        {
            if (func == null)
                throw new ArgumentNullException("func");

            if (completition == null)
                throw new ArgumentNullException("completition");

            var cts = new CancellationTokenSource();
            var token = cts.Token;

            var scheduler = TaskScheduler.FromCurrentSynchronizationContext();

            var task = new Task<TOut>(() => func(parameter), TaskCreationOptions.LongRunning);
            task.ContinueWith(asyncPartTask => onException(asyncPartTask.Exception), CancellationToken.None, TaskContinuationOptions.OnlyOnFaulted, scheduler);
            task.ContinueWith(asyncPart =>
            {
                if (!token.IsCancellationRequested)
                    completition();
            },
                              CancellationToken.None, TaskContinuationOptions.OnlyOnRanToCompletion, scheduler);
            task.Start();

            return cts;
        }

        public static void ExecuteBlockingOperation(Action action, Action completition, Func<bool> shouldComplete, Action<AggregateException> onException)
        {
            if (action == null)
                throw new ArgumentNullException("action");

            if (completition == null)
                throw new ArgumentNullException("completition");

            var scheduler = TaskScheduler.FromCurrentSynchronizationContext();

            var task = new Task(action, TaskCreationOptions.LongRunning);
            task.ContinueWith(asyncPartTask => onException(asyncPartTask.Exception), CancellationToken.None, TaskContinuationOptions.OnlyOnFaulted, scheduler);
            task.ContinueWith(asyncPart =>
                                  {
                                      if (shouldComplete == null || shouldComplete())
                                          completition();
                                  },
                              CancellationToken.None, TaskContinuationOptions.OnlyOnRanToCompletion, scheduler);
            task.Start();
        }

        public static void ExecuteBlockingOperation<TIn>(Action<TIn> action, TIn parameter, Action<TIn> completition, Predicate<TIn> shouldComplete, Action<AggregateException, TIn> onException)
        {
            if (action == null)
                throw new ArgumentNullException("action");

            if (completition == null)
                throw new ArgumentNullException("completition");

            var scheduler = TaskScheduler.FromCurrentSynchronizationContext();

            var task = new Task(() => action(parameter), TaskCreationOptions.LongRunning);
            task.ContinueWith(asyncPartTask => onException(asyncPartTask.Exception, parameter), CancellationToken.None, TaskContinuationOptions.OnlyOnFaulted, scheduler);
            task.ContinueWith(asyncPart =>
                                  {
                                      if (shouldComplete == null || shouldComplete(parameter))
                                          completition(parameter);
                                  },
                              CancellationToken.None, TaskContinuationOptions.OnlyOnRanToCompletion, scheduler);
            task.Start();
        }

        public static void ExecuteBlockingOperation<TOut>(Func<TOut> func, Action<TOut> completition, Predicate<TOut> shoudComplete, Action<AggregateException> onException)
        {
            if (func == null)
                throw new ArgumentNullException("func");

            if (completition == null)
                throw new ArgumentNullException("completition");

            var scheduler = TaskScheduler.FromCurrentSynchronizationContext();

            var task = new Task<TOut>(func, TaskCreationOptions.LongRunning);
            task.ContinueWith(asyncPartTask => onException(asyncPartTask.Exception), CancellationToken.None, TaskContinuationOptions.OnlyOnFaulted, scheduler);
            task.ContinueWith(asyncPartTask =>
                                  {
                                      if (shoudComplete == null || shoudComplete(asyncPartTask.Result))
                                          completition(asyncPartTask.Result);
                                  },
                              CancellationToken.None, TaskContinuationOptions.OnlyOnRanToCompletion, scheduler);
            task.Start();
        }

        public static void ExecuteBlockingOperation<TIn, TOut>(Func<TIn, TOut> func, TIn parameter, Action<TOut, TIn> completition, Func<TOut, TIn, bool> shouldComplete, Action<AggregateException, TIn> onException)
        {
            if (func == null)
                throw new ArgumentNullException("func");

            if (completition == null)
                throw new ArgumentNullException("completition");

            var scheduler = TaskScheduler.FromCurrentSynchronizationContext();

            var task = new Task<TOut>(() => func(parameter), TaskCreationOptions.LongRunning);
            task.ContinueWith(asyncPartTask => onException(asyncPartTask.Exception, parameter), CancellationToken.None, TaskContinuationOptions.OnlyOnFaulted, scheduler); // on Exception
            task.ContinueWith(asyncPart =>
                                  {
                                      if (shouldComplete == null || shouldComplete(asyncPart.Result, parameter))
                                          completition(asyncPart.Result, parameter);
                                  },
                              CancellationToken.None, TaskContinuationOptions.OnlyOnRanToCompletion, scheduler);
            task.Start();
        }            
    }

- Pavel Voronin

Answer 3

使用Task.ContinueWith，它会在任务完成后执行您的操作。

以下是一些有用的示例：

http://msdn.microsoft.com/en-us/library/dd784422.aspx

- sam1589914