当应用程序在后台时，在不调用DidReceiveRemoteNotification的情况下显示NotificationHub的Xamarin iOS通知

using Foundation;
using UIKit;
using Microsoft.Azure.NotificationHubs;

namespace YourAppNamespace
{
    [Register("AppDelegate")]
    public class AppDelegate : UIApplicationDelegate
    {
        public override bool FinishedLaunching(UIApplication application, NSDictionary launchOptions)
        {
            // 注册设备
            RegisterForRemoteNotifications();

            return true;
        }

        public override void RegisteredForRemoteNotifications(UIApplication application, NSData deviceToken)
        {
            // 获取设备标识符
            var hub = new SBNotificationHub("<connection string>", "<hub name>");
            hub.RegisterNativeAsync(deviceToken, null, error =>
            {
                if (error != null)
                {
                    // 注册失败
                }
                else
                {
                    // 注册成功
                }
            });
        }

        public override void DidReceiveRemoteNotification(UIApplication application, NSDictionary userInfo, Action<UIBackgroundFetchResult> completionHandler)
        {
            // 处理推送通知
            // 在这里可以获取通知的内容，并根据需要执行相应的操作
            // 例如显示通知、更新UI等
        }

        private void RegisterForRemoteNotifications()
        {
            if (UIDevice.CurrentDevice.CheckSystemVersion(10, 0))
            {
                UNUserNotificationCenter.Current.RequestAuthorization(UNAuthorizationOptions.Alert | UNAuthorizationOptions.Sound | UNAuthorizationOptions.Badge, (granted, error) =>
                {
                    if (granted)
                    {
                        InvokeOnMainThread(UIApplication.SharedApplication.RegisterForRemoteNotifications);
                    }
                });
            }
            else if (UIDevice.CurrentDevice.CheckSystemVersion(8, 0))
            {
                var settings = UIUserNotificationSettings.GetSettingsForTypes(UIUserNotificationType.Alert | UIUserNotificationType.Sound | UIUserNotificationType.Badge, null);
                UIApplication.SharedApplication.RegisterUserNotificationSettings(settings);
                UIApplication.SharedApplication.RegisterForRemoteNotifications();
            }
        }
    }
}