带signalR的SqlNotificationEvents会导致多次触发？

Question

我是新手，在asp.net mvc项目中使用signalr来捕获用户通知。我跟着these steps

这是我的ajax电话

$(function () {

        // Proxy created on the fly
        var job = $.connection.ntfHub;

        // Declare a function on the job hub so the server can invoke it
        job.client.displayStatus = function () {
            toastr.warning("1 Bildirim Alındı!");
            getData();
        };

        // Start the connection
        $.connection.hub.start().done(function () {
            console.log("connection started")
            getData();
        }).fail(function (e) {
            alert(e);
        });
    });

    function getData() {
        var tbl = $("#header_notification_bar")
         $.ajax({
            url: '@Url.Action("GetNtf","Home")',
            contentType: 'application/html ; charset:utf-8',
            type: 'GET',
            dataType: 'html'
        }).success(function (result) {
            tbl.empty().append(result);
            console.log("called");
        }).error(function () {

        });


    }

这是我的SQL查询

SELECT 
    [nu].[NtU_ID], [n].[Ntf_Title], [n].[Ntf_Description],
    [u].[Usr_NameSurname], [n].[Ntf_Date] 
FROM 
    [dbo].[SysNotificationUser] nu 
INNER JOIN  
    [dbo].[SysUser] u ON [nu].[NtU_UserID] = [u].[ID] 
INNER JOIN 
    [dbo].[SysNotifications] n ON [nu].[NtU_NtfID] = [n].[Ntf_ID] 
WHERE 
    [nu].[NtU_UserID] = 2 
    AND [nu].[NtU_IsRead] = 0

关于使用信号器如启动类的其他问题与教程中的相同。

有一些奇怪的情况第一次发生变化时ajax发出1个电话但其他变化ajax电话变得越来越大。除第一次以外，它不会进行1次更改。例如在控制台中，第一次只有一个“被叫”，但之后就像8次被“召唤”16次“被叫”等等。

在存储库中

private void dependency_OnChange(object sender, SqlNotificationEventArgs e)
    {
        if (e.Type == SqlNotificationType.Change)
        {
            NtfHub.Show();
        }

    }

和Hub类

public void Hello()
    {
        Clients.All.hello();
    }
    [HubMethodName("show")]
    public static void Show()
    {
        IHubContext context = GlobalHost.ConnectionManager.GetHubContext<NtfHub>();
        context.Clients.All.displayStatus();
    }

执行命令的方法

 public List<PopulateNtfBar> GetData()
    {

        DataTable dt = new DataTable();
        using (var connection = new SqlConnection(ConfigurationManager.ConnectionStrings["conn"].ConnectionString))
        {
            connection.Open();
            using (SqlCommand command = new SqlCommand(@"SELECT [NtU_ID] FROM [dbo].[SysNotificationUser] WHERE [NtU_UserID] =2 AND [NtU_IsRead] = 0", connection))
            {
                // Make sure the command object does not already have
                // a notification object associated with it.
                command.Notification = null;

                SqlDependency dependency = new SqlDependency(command);
                dependency.OnChange += dependency_OnChange;

                if (connection.State == ConnectionState.Closed)
                    connection.Open();
                    command.ExecuteScalar();

            }

            using (SqlCommand command2 = new SqlCommand(@"SELECT [nu].[NtU_ID],[n].[Ntf_Title],[n].[Ntf_Description],[u].[Usr_NameSurname],[n].[Ntf_Date] FROM [dbo].[SysNotificationUser] nu INNER JOIN [dbo].[SysUser] u ON [nu].[NtU_UserID]=[u].[ID] INNER JOIN [dbo].[SysNotifications] n ON [nu].[NtU_NtfID]=[n].[Ntf_ID] WHERE [nu].[NtU_UserID] =2 AND [nu].[NtU_IsRead] = 0", connection))
            {
                using (var reader = command2.ExecuteReader())
                    return reader.Cast<IDataRecord>()
                        .Select(item => new PopulateNtfBar()
                        {
                            Description = item["Ntf_Description"].ToString(),
                            Title = item["Ntf_Title"].ToString(),
                            TimeDiff = FindDifferenceTime(Convert.ToDateTime(item["Ntf_Date"]))
                        }).ToList();


            }
        }
    }