在ContinueWith()块中使用await [英] Using await inside a ContinueWith() block

问题描述

我有以下代码:

var result = MessageBoxHelper.MsgBox
    .ShowAsync("Press Yes to proceed", MessageBoxButton.YesNo)
    .ContinueWith((answer) =>
    {
        if (answer.Result == MessageBoxResult.Yes)
        {
            Task<bool> asyncTask = ExecuteAsyncFunc();
            //asyncTask.Unwrap(); ??
            asyncTask.ContinueWith((a) =>
            {
                // More 
            }, TaskContinuationOptions.OnlyOnRanToCompletion);
        }
    }, TaskContinuationOptions.OnlyOnRanToCompletion);
}

在其他地方这样调用:

public async Task<bool> ExecuteAsyncFunc()
{
    await CallAnotherAsyncFunction();
}

我相信我需要在试图调用的地方调用Unwrap()，因为我正在ContinueWith()块内调用await.但是，取消注释时会出现以下错误:

I believe that I need to call Unwrap(), where I have tried to, because I am calling await inside a ContinueWith() block. However, I get the following error when I uncomment it:

错误CS1929任务"不包含展开"的定义 最好的扩展方法重载 'TaskExtensions.Unwrap(Task)'需要一个类型的接收器 任务"

Error CS1929 'Task' does not contain a definition for 'Unwrap' and the best extension method overload 'TaskExtensions.Unwrap(Task)' requires a receiver of type 'Task'

我是否需要在这种情况下使用Unwrap?如果是，我在做什么错了?

Do I need to use Unwrap in this context, and if so, what am I doing wrong?

推荐答案

简短的答案是使用await代替ContinueWith:

The short answer is to use await instead of ContinueWith:

var result = MessageBoxHelper.MsgBox.ShowAsync("Press Yes to proceed", MessageBoxButton.YesNo);
if (answer == MessageBoxResult.Yes)
{
  var a = await ExecuteAsyncFunc();
  // More 
}

长答案是 ContinueWith具有某些危险的默认值选项(包括使用环境TaskScheduler)和await自动为您正确执行所有操作.我会在博客上详细介绍.

The long answer is that ContinueWith has some dangerous default options (including using an ambient TaskScheduler), and await automatically does everything correctly for you. I go into more detail on my blog.

这篇关于在ContinueWith()块中使用await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！