'Async push notification to Microsoft Authenticator App”改为“将异步推送通知到 Microsoft Authenticator 应用程序”，实现方法如下所示：

首先需要安装 Microsoft 的推送通知服务 NuGet 包。在代码中创建一个 PushModel，包含推送内容信息。然后创建一个 PushHub 来执行消息的实际推送，并通过 Microsoft 帐号的用户 ID 检查已注册 Authenticator 应用程序的用户。最后，将推送通知对象序列化为 JSON 字符串并推送到 Microsoft。示例代码如下：

using Microsoft.AspNet.SignalR;
using Microsoft.AspNet.SignalR.Hubs;

namespace PushNotificationDemo
{
    public class PushModel
    {
        public string UserId { get; set; }
        public string Title { get; set; }
        public string Message { get; set; }
        public string Data { get; set; }
    }

    [HubName("pushHub")]
    public class PushHub : Hub
    {
        public void PushNotification(PushModel model)
        {
            var pushService = new PushService();
            pushService.Push(model);
        }
    }

    public class PushService
    {
        public async Task Push(PushModel model)
        {
            var microsoftUrl = "https://login.microsoftonline.com/common/oauth2/token";
            var clientId = "";
            var clientSecret = "";
            var authenticatorUrl = "https://graph.microsoft.com/v1.0/me/appRoleAssignedTo";
            var tokensUrl = "https://graph.microsoft.com/v1.0/me/microsoft.graph.get";

            var token = await GetAccessToken(microsoftUrl, clientId, clientSecret);

            var authenticatorService = new AuthenticatorService();
            var userId = authenticatorService.GetRegisteredUserId(token, authenticatorUrl);

            if (string.IsNullOrEmpty(userId))
            {
                // Throw exception here or handle it as per requirement
            }

            var pushNotification = new PushNotification();
            pushNotification.PushUserId = userId;
            pushNotification.Title = model.Title;
            pushNotification.Message = model.Message