如何等待RequestAccessAsync？

我試圖創建一個監聽器到Windows的通知，下面就this example on Micr*soft's blog 如何等待RequestAccessAsync？

非常第二代碼剪斷的步驟，理應得到用戶授權，不編譯說：

error CS4033: The 'await' operator can only be used within an async method. 
Consider marking this method with the 'async' modifier and changing its return type to 'Task'.

雖然我不熟悉C＃的異步/等待機制，該方法的問題叫做RequestAccess 異步，並且由Visual Studio打開的源在方法上方有一個[RemoteAsync]。

這是一個完整的代碼剪斷：

// Get the listener 
UserNotificationListener listener = UserNotificationListener.Current; 

// And request access to the user's notifications (must be called from UI thread) 
UserNotificationListenerAccessStatus accessStatus = await listener.RequestAccessAsync(); 

switch (accessStatus) 
{ 
    // This means the user has granted access. 
    case UserNotificationListenerAccessStatus.Allowed: 

     // Yay! Proceed as normal 
     break; 

    // This means the user has denied access. 
    // Any further calls to RequestAccessAsync will instantly 
    // return Denied. The user must go to the Windows settings 
    // and manually allow access. 
    case UserNotificationListenerAccessStatus.Denied: 

     // Show UI explaining that listener features will not 
     // work until user allows access. 
     break; 

    // This means the user closed the prompt without 
    // selecting either allow or deny. Further calls to 
    // RequestAccessAsync will show the dialog again. 
    case UserNotificationListenerAccessStatus.Unspecified: 

     // Show UI that allows the user to bring up the prompt again 
     break; 
}

我怎樣才能解決這個問題？

來源

2017-05-29 RSFalcon7

哪裏是你的方法的簽名？你把它標記爲「異步」嗎？ –

你需要展示更多的代碼，你需要展示保存你的代碼示例的方法， –

感謝那些問題。這段代碼是在一個類的構造函數中，（正如我剛學到的，不能是異步的） – RSFalcon7

這不是完整的代碼片段...您需要將調用方法標記爲async。

public async Task<ReturnType> MyMethod() 
{ 
    // Get the listener 
    UserNotificationListener listener = UserNotificationListener.Current; 

    // And request access to the user's notifications (must be called from UI thread) 
    UserNotificationListenerAccessStatus accessStatus = await listener.RequestAccessAsync(); 
}

爲此在構造函數中，按您的意見，我會用Nito.AsyncEx和AsyncContext這樣的：

public class MyProgram 
{ 
    public MyProgram() 
    { 
     UserNotificationListenerAccessStatus accessStatus = AsyncContext.Run(listener.RequestAccessAsync); 
    } 
}

來源

2017-05-29 19:38:46

如何等待RequestAccessAsync？

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