我有thread中提到的类似问题,根据Stephen Cleary的评论,WinRT的解决方案是使用延期。线程中指出的解决方案也适用于我,但我想尝试使用延迟,因为它可能是或成为处理这种情况的标准方法。
所以我读了他的blog并尝试将其应用到我的代码中,但我似乎无法让它工作。发生的事情是仍然没有等待事件订阅。我也找不到任何可以运行和分析的完整示例程序。所以我尝试创建一个示例控制台程序来演示我所看到的问题。
首先,我有事件处理程序委托和事件参数定义:
public delegate void CancelEventHandlerAsync(object sender, CancelEventArgsAsync e);
public class CancelEventArgsAsync : CancelEventArgs
{
private readonly DeferralManager _deferrals = new DeferralManager();
public IDisposable GetDeferral()
{
return this._deferrals.GetDeferral();
}
public Task WaitForDefferalsAsync()
{
return this._deferrals.SignalAndWaitAsync();
}
}
然后是作为事件发送者的子模块定义:
public class ChildModule1
{
public event CancelEventHandlerAsync ChildModuleLaunching;
public async Task Launch()
{
var cancelEventArgs = new CancelEventArgsAsync();
this.ChildModuleLaunching(this, cancelEventArgs);
cancelEventArgs.WaitForDefferalsAsync();
if (cancelEventArgs.Cancel)
{
return;
}
Console.WriteLine("Child module 1 launched."); // This should not be executed.
}
}
然后订阅子模块事件的父类:
public class Parent
{
private ChildModule1 child1 = new ChildModule1();
public Parent()
{
this.child1.ChildModuleLaunching += this.OnChildModule1Launching;
}
public async Task Process()
{
await this.child1.Launch();
}
private async void OnChildModule1Launching(object sender, CancelEventArgsAsync e)
{
var deferral = e.GetDeferral();
await Task.Delay(2500); // Simulate processing of an awaitable task.
e.Cancel = true;
deferral.Dispose();
}
}
最后,控制台应用入口点:
static void Main(string[] args)
{
var parent = new Parent();
parent.Process().Wait();
Console.ReadKey();
}
答案 0 :(得分:2)
您需要await
WaitForDefferalsAsync
来电:
await cancelEventArgs.WaitForDefferalsAsync();