问题
I am using Visual Studio 2017 Professional.
I have been following this guide: https://docs.microsoft.com/en-us/windows/uwp/design/shell/tiles-and-notifications/notification-listener
My problem code is as follows:
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using Windows.UI.Notifications;
using System;
namespace SeleniumWebChat.Utilities
{
// This class handles Windows 'Toast' notifications that pop up when a new webchat/call is received
static class WinNotificationHandler
{
static async Task<bool> TaskCheckWinNotification(string notifType, string guest)
{
Windows.UI.Notifications.Management.UserNotificationListener listener = Windows.UI.Notifications.Management.UserNotificationListener.Current;
//only read notifications if we have access - this may need to be set in windows settings
if (listener.GetAccessStatus().ToString() == "Allowed")
{
// Get the windows toast notifications as a list
IReadOnlyList<UserNotification> notifs = await listener.GetNotificationsAsync(NotificationKinds.Toast);
//Console.Error.WriteLine("number of notifications found: " + notifs.Count());
}
return false;
}
}
}
The problem is with this line:
IReadOnlyList<UserNotification> notifs = await listener.GetNotificationsAsync(NotificationKinds.Toast);
Which gives the error:
'IAsyncOperation<IReadOnlyList<UserNotification>>'does not contain a definition for 'GetAwaiter' and no extension method 'GetAwaiter' accepting a first argument of type'IAsyncOperation<IReadOnlyList<UserNotification>>'could be found (are you missing a using directive for 'System'?)
I've tried everything I can find online, from adding references to:
- C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework.NETCore\v4.5\System.Runtime.WindowsRuntime.dll
- C:\Program Files (x86)\Windows Kits\10\UnionMetadata\Facade\Windows.WinMD
To adding NuGet packages:
- UwpDesktop
- Microsoft.NETCore.UniversalWindowsPlatform
To reinstalling VS and trying different versions of the SDK.
I really have no idea what is causing this issue, I would be very grateful for any pointers in the right direction.
回答1:
You should add
using System.WindowsRuntimeSystemExtensions;
this is from the System.Runtime.WindowsRuntime assembly and holds a class with the GetAwaiter extensions.
来源：https://stackoverflow.com/questions/54515716/iasyncoperationireadonlylistusernotification-does-not-contain-a-definition