signalr with sqldepdency firing multiple times for each browser instance - asp.net-mvc-4

Question

I am having a asp.net mvc app with vs2013 and .net framwork 4.5.1 which should notify users when a certain field gets updated and for a certain recordID.
Everything works fine when I have a single instance of the browser open, but when i open another tab or browser either on the same machine or on the different machine it fires the sqldepdencychange event multiple times.
Below is my hub code
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);
}
}
Below is my signalr script file
$(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();
};
Below is my partialview code along with the definition for RegisterForNotification and depdendency_onchange event
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);
}
Not sure why it is firing the sendmessages multiple times with each additional browser instance that I open. Any pointers would be helpful!

Answer 1

remove EventHandler when you done with it
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);
}