Question

我想做

async Task DoSomething()
{
   await SomeAsyncAPI();
}

async void Run()
{
   await DoSomething();
   DoAnother();
}

但IBackgroundTask类中不允许使用任务类型。我想在DoSomething完成后运行DoAnother（）。

Answer 1

您可以使用等待的IAsyncAction和WindowsRuntimeSystemExtensions.AsAsyncAction：

public IAsyncAction DoWorkAction()
{
    return DoWorkAsync().AsAsyncAction();
}

internal async Task DoWorkAsync()
{
    await Task.Delay(100);
}

public async void Run(IBackgroundTaskInstance taskInstance)
{
   var deferral = taskInstance.GetDeferral();
   try
   {
      await DoWorkAction();
      DoAnother();
   }
   finally
   {
      deferral.Complete();
   }
}

对于Task<T>，请使用IAsyncOperation<T>：

public IAsyncOperation<string> DoMoreWorkAction()
{
    return DoMoreWorkAsync().AsAsyncOperation();
}

internal async Task<string> DoMoreWorkAsync()
{
    await Task.Delay(1000);
    return "Hello";
}

public async void Run(IBackgroundTaskInstance taskInstance)
{
   var deferral = taskInstance.GetDeferral();
   try
   {
      await DoMoreWorkAction();
      DoAnother();
   }
   finally
   {
      deferral.Complete();
   }
}

Answer 2

要将异步方法与WinRT命令样式事件（包括IBackgroundTask.Run）一起使用，您需要使用deferrals：

async void Run(IBackgroundTaskInstance instance)
{
  var deferral = instance.GetDeferral();
  try
  {
    await DoSomething();
    DoAnother();
  }
  finally
  {
    deferral.Complete();
  }
}

IBackgroundTask类中的任务类型

2 个答案: