c# - 如何在 asp.net C# 4.0 中调用异步方法？

Question

我知道 .net 4.5 有 await, async 关键字，可以轻松调用异步方法。我目前正在研究如何在 C# 4.0 中进行异步调用。我想要的一个例子是在数据网格被数据绑定的地方进行异步调用。

如果您能给我一些链接，我将不胜感激。

Answer 1

看看使用任务，这在 .Net 4 中可用，应该对您有所帮助。一个简单的示例可能如下所示：

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
}

更多，看这里

Answer 2

使用 Task.ContinueWith 在任务完成后基本上执行您的操作。

一些可能有用的例子：

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

Answer 3

我们制作了一些用于执行异步操作的工具类。

这些方法的真正作用是：异步执行操作，然后将完成的执行相应地发布到同步上下文。

我们将其作为 TPL 的包装器，以便在我们调用长时间运行的操作时在 WPF 中轻松使用它。这个类也有类似的动作可以取消，而不仅仅是放弃。

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();
        }            
    }