相关疑难解决方法(0)

使用Microsoft for .NET的异步CTP,是否可以捕获调用方法中异步方法抛出的异常？

public async void Foo()
{
    var x = await DoSomethingAsync();

    /* Handle the result, but sometimes an exception might be thrown.
       For example, DoSomethingAsync gets data from the network
       and the data is invalid... a ProtocolException might be thrown. */
}

public void DoFoo()
{
    try
    {
        Foo();
    }
    catch (ProtocolException ex)
    {
          /* The exception will never be caught.
             Instead when in debug mode, VS2010 will warn and continue.
             The deployed the app will simply crash. …

我正在尝试基于VS2013项目模板中的示例AccountController为ASP.NET MVC5网站设置电子邮件确认.我已经实现了IIdentityMessageService使用SmtpClient,试图尽可能简单:

public class EmailService : IIdentityMessageService
{
    public async Task SendAsync(IdentityMessage message)
    {
        using(var client = new SmtpClient())
        {
            var mailMessage = new MailMessage("some.guy@company.com", message.Destination, message.Subject, message.Body);
            await client.SendMailAsync(mailMessage);
        }
    }
}

调用它的控制器代码直接来自模板(由于我想排除其他可能的原因,因此将其解压缩为单独的操作):

public async Task<ActionResult> TestAsyncEmail()
{
    Guid userId = User.Identity.GetUserId();

    string code = await UserManager.GenerateEmailConfirmationTokenAsync(userId);
    var callbackUrl = Url.Action("ConfirmEmail", "Account", new { userId = userId, code = code }, protocol: Request.Url.Scheme);
    await UserManager.SendEmailAsync(userId, "Confirm your account", "Please confirm your account by clicking <a …

我需要一些帮助来找出问题所在.我已经使用了ASP.NET核心,我对此非常熟悉,尽管.NET核心C#似乎在"崩溃"并且在尝试发出异步请求时退出.

我有一个返回系统外部IP的方法

private async Task<string> getExternalIP()
    {
        using (System.Net.Http.HttpClient HC = new System.Net.Http.HttpClient())
        {
            return await HC.GetStringAsync("https://api.ipify.org/");
        }

    }

这应该可以工作,但是当它到达HC.GetStringAsync时会退出.我也试过在它上面设一个断点,但它实际上并没有运行.

我试图通过使用调用该方法

string Address = await getExternalIP();

任何帮助都很感激,希望我不只是忽略了一些东西.

谢谢!

摘自Stephen Cleary关于异步等待的文章:

图2异步无效方法的异常无法通过Catch捕获

private async void ThrowExceptionAsync()
{
  throw new InvalidOperationException();
}
public void AsyncVoidExceptions_CannotBeCaughtByCatch()
{
  try
  {
    ThrowExceptionAsync();
  }
  catch (Exception)
  {
    // The exception is never caught here!
    throw;
  }
}

...异步void方法抛出的任何异常将直接在异步void方法启动时处于活动状态的SynchronizationContext上引发...

这究竟意味着什么？我写了一个扩展示例来尝试收集更多信息.它具有与图2相同的行为:

static void Main()
{

    AppDomain.CurrentDomain.UnhandledException += (sender, ex) => 
    {
        LogCurrentSynchronizationContext("AppDomain.CurrentDomain.UnhandledException");
        LogException("AppDomain.CurrentDomain.UnhandledException", ex.ExceptionObject as Exception);
    };

    try
    {
        try
        {
            void ThrowExceptionVoid() => throw new Exception("ThrowExceptionVoid");

            ThrowExceptionVoid();
        }
        catch (Exception ex)
        {
            LogException("AsyncMain - Catch - ThrowExceptionVoid", ex);
        }

        try
        {
            // CS1998 …

我有以下场景:
当输入命令时(为了测试,它是一个控制台应用程序,当它准备就绪时,我希望它将是一个WebService)我执行一些代码,当需要进一步的用户输入时,我返回命令立即翻译.当给出新输入时,我希望处理从我离开它的地方继续.这听起来很像c#5 async-await模式,我决定尝试一下.我在想这个:

public void CommandParser()
{
   while(true)
   { 
      string s = Console.ReadLine();
      if (s == "do_something")
         Execute();
      else if (s == "give_parameters")
         SetParameters();
      //... 
   }
}
MySettings input;
public async void Execute()
{
  //do stuff here
  MyResult result = null
  if (/*input needed*/){
     input = new MySetting();
     result = await input.Calculate();
  }
  else { /* fill result synchronously*/}
  //do something with result here

}

public void SetParameters()
{
   if (input!=null)
      input.UseThis("something"); //now it can return from await
}

现在我的问题是,如何编写MySettings.Calculate和MySettings.UseThis？如何从第一个返回任务以及如何从第二个发出准备信号？我已尝试过许多工厂方法的Task,但我找不到合适的方法!请帮忙!