在同步方法异步调用 [英] Asynchronous call in synchronous method

问题描述

下面是一个简单的例子：

Here is the simple example:

public event EventHandler CookinDone = delegate{};

public void CoockinRequest(){
    var indicator = new ActivityIndicator();
    ActivityIndicator.Show("Oooo coockin' something cool");

    var bw = new BackgroundWorker();    
    bw.DoWork += (sender, e) => CockinService.Cook();
    bw.RunWorkerCompleted += (sender, e) => {
       indicator.Hide();
       CookinDone.Invoke(this,null);
    };

    bw.RunWorkerAsync();
}

现在，每次我用这个方法我要拦截CookinDone事件和移动

Now, everytime I use that method I have to intercept CookinDone event and move on.

var cook = new Cook();
cook.CookinDone += (sender, e) => MessageBox.Show("Yay, smells good");
cook.CoockinRequest();

但我怎么能简化，通过使该方法布尔返回类型的，对乱打返回结果？完成

But how can I simplify that by making return type of the method as Boolean and return result upon the Cookin completion?

if (CoockinRequest()) MessageBox.Show('Yay, smells even better');

如果我把有类似而（bw.IsBusy）它会搞砸我的ActivityIndi​​cator，冻结主线程，我觉得这是做那么最蹩脚的事情。也有一些 Monitor.Wait 的东西和一些其他的东西，比如 TaskFactory ，但所有的东西似乎太复杂在简单的方案中使用。

if I put there something like while (bw.IsBusy) it will screw my ActivityIndicator, freeze the main thread and I feel it would be the lousiest thing to do. There are also some Monitor.Wait stuff and some other stuff like TaskFactory, but all that stuff seems to be too complicated to use in simple scenarios.

这可能是在不同的环境也不同，像一些做法是很好的WPF应用程序，有的为别人和诸如此类的东西，但东西应该有一个一般的模式是不对吧？

It might be also different in different environments, like some approach is good for WPF apps, some for something else and whatnot, but there should be a general pattern isn't that right?

你怎么做男人？

推荐答案

没有一个直接的方式在.NET 4这实际上是在与新的异步线路非常要这样做/等待功能在C＃中的下一个版本的到来。

There isn't a direct way to do this in .NET 4. This is actually very much in line with the new async/await functionality coming in the next release of C#.

任务并行库可以在.NET 4中使用该今天完成。布尔> ，所以调用者可以等待就可以了（如果需要），或认购一个的继续任务<做到这一点。就当这是完成这将运行任务EM>

The Task Parallel Library can be used in .NET 4 to accomplish this today. You would do this by changing your code to return a Task<bool>, so the caller could wait on it (if required), or subscribe a continuation on the task which would run when this was complete.

要做到这一点，你会重写上面的代码如下所示：

To do this, you'd rewrite the above code like so:

public Task<bool> CoockinRequestAsync()
{
    var indicator = new ActivityIndicator();
    ActivityIndicator.Show("Oooo coockin' something cool");

    // This assumes Cook() returns bool...
    var task = Task.Factory.StartNew(CockinService.Cook);

    // Handle your removal of the indicator here....
    task.ContinueWith( (t) => 
       {
           indicator.Hide();
       }, TaskScheduler.FromCurrentSynchronizationContext());

    // Return the task so the caller can schedule their own completions
    return task;
}

然后，当你去使用它，你会写类似：

Then, when you go to use this, you'd write something like:

private void SomeMethod()
{
    var request = this.CoockinRequestAsync();

    request.ContinueWith( t =>
    {
        // This will run when the request completes... 
        bool result = t.Result;

        // Use result as needed here, ie: update your UI

    }, TaskScheduler.FromCurrentSynchronizationContext());
}

这篇关于在同步方法异步调用的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！