Question

我正在使用带有vs2013和.net framwork 4.5.1的asp.net mvc应用程序，该应用程序应该在某个字段更新时通知用户以及某个recordID。当我打开一个浏览器实例时，一切正常，但是当我在同一台机器或不同的机器上打开另一个选项卡或浏览器时，它会多次触发sqldepdencychange事件。

以下是我的中心代码

public class MessagesHub : Hub
    {
        private static string conString = ConfigurationManager.ConnectionStrings["FleetLink_DB"].ToString();

        private static string hostName = "";


        public static void SendMessages(string hName)
        {
            IHubContext context = GlobalHost.ConnectionManager.GetHubContext<MessagesHub>();
            hostName = hName;
            context.Clients.Group(hostName).updateMessages(hName);
        }

        public Task leaveGroup(string hName)
        {
            return Groups.Remove(Context.ConnectionId, hName);
        }

        public Task joinGroup(string hName)
        {
            return Groups.Add(Context.ConnectionId, hName);
        }
}

以下是我的信号员脚本文件

  $(function () {
            var dialog, form
            // Declare a proxy to reference the hub.

            var notifications = $.connection.messagesHub;
            //debugger;
            //Create a function that the hub can call to broadcast messages.
            notifications.client.updateMessages = function (hName) {
                alert("testing");
                getoneMessages(hName)
            };

            $.connection.hub.logging = true;
            $.connection.hub.start().done(function () {
                var hostName = getUrlVars()["System_Name"];
                notifications.server.joinGroup(hostName);
            }).fail(function (e) {
                alert(e);
            });
        });

        function getUrlVars() {
            var vars = [], hash;
            var hashes = window.location.href.slice(window.location.href.indexOf('?') + 1).split('&');
            for (var i = 0; i < hashes.length; i++) {
                hash = hashes[i].split('=');
                vars.push(hash[0]);
                vars[hash[0]] = hash[1];
            }
            return vars;
        }

        function getoneMessages(hName) {
            var tbl = $('#selectable');
            //alert('mesgID=' + mesgID)
            //var tbl = $('#selectable');
            $.ajax({
                url: '/controller/view',
                cache: false,
                contentType: 'application/html ; charset:utf-8',
                type: 'GET',
                dataType: 'html'
            }).success(function (result) {
                //alert(result);
                tbl.empty().append(result);
            }).error(function (exception) {
                //alert('failed= ' + exception);
            });
        }

        window.onbeforeunload = function (e) {
            var hostName = getUrlVars()["System_Name"];
            notifications.server.joinGroup(hostName);
            $.connection.hub.stop();

        };

下面是我的partialview代码以及RegisterForNotification和depdendency_onchange事件的定义

public PartialViewResult SignalRTesterPartialView()
{
 /...COde not included for brevity..../
   RegisterForNotifications(ID);
}



public void RegisterForNotifications(int mID)
        {
            var efConnectionString = ConfigurationManager.ConnectionStrings["DB"].ConnectionString;
            var builder = new EntityConnectionStringBuilder(efConnectionString);
            var regularConnectionString = builder.ProviderConnectionString;

            string commandText = null;


            commandText = "select ID,Status,Name from tblABC where ID=" + strID;

                using (SqlConnection connection = new SqlConnection(regularConnectionString))
                {
                    using (SqlCommand command = new SqlCommand(commandText, connection))
                    {
                        connection.Open();

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

                        // NOTE: You have to execute the command, or the notification will never fire.
                        var reader = command.ExecuteReader();
                    }
                }

        }

        private void dependency_OnChange(object sender, SqlNotificationEventArgs e)
        {
            if (e.Type == SqlNotificationType.Change && e.Info== SqlNotificationInfo.Update)
            {
                MessagesHub.SendMessages(hName);
            }

            RegisterForNotifications(1012);


        }

不确定为什么它会在我打开的每个其他浏览器实例中多次触发sendmessages。任何指针都会有所帮助！

Answer 1

完成后删除EventHandler

private void dependency_OnChange(object sender, SqlNotificationEventArgs e)
{
    if (e.Type == SqlNotificationType.Change && e.Info== SqlNotificationInfo.Update)
    {
        MessagesHub.SendMessages(hName);
    }

    //remove event handler
    SqlDependency dependency = sender as SqlDependency;
    dependency.OnChange -= new OnChangeEventHandler(dependency_OnChange);

    RegisterForNotifications(1012);
}

每个浏览器实例多次触发sqldepdency的signalr

1 个答案: