public class User
{
public string UserName { get; set; }
public bool IsRole { get; set; }
public HashSet<string> ConnectionIds { get; set; }
}
[Authorize]
[HubName("userActivityHub")]
public class UserActivityHub : Hub
{
private static readonly ConcurrentDictionary<string, User> Users = new ConcurrentDictionary<string, User>();
public void AdminJoin()
{
Groups.Add(Context.ConnectionId, "admins");
}
public void Join()
{
var userName = Context.User.Identity.Name;
var connectionId = Context.ConnectionId;
var isAdmin = Context.User.IsInRole("Admin");
var user = Users.GetOrAdd(userName, _ => new User
{
UserName = userName,
IsRole = isAdmin,
ConnectionIds = new HashSet<string>()
});
if (user.IsRole == true)
{
Groups.Add(user.ConnectionIds.ToString(), "admins");
}
else
{
lock (user.ConnectionIds)
{
user.ConnectionIds.Add(connectionId);
}
Clients.Group("admins").showUserCount(Users.Count(a => a.Value.IsRole != true));
}
}
public void GetUserCount()
{
Clients.Group("admins").showUserCount(Users.Count(a => a.Value.IsRole != true));
}
public override System.Threading.Tasks.Task OnDisconnected(bool stopCalled)
{
if (stopCalled)
{
var userName = Context.User.Identity.Name;
var connectionId = Context.ConnectionId;
User user;
Users.TryGetValue(userName, out user);
if (user != null)
{
lock (user.ConnectionIds)
{
user.ConnectionIds.RemoveWhere(cid => cid.Equals(connectionId));
if (!user.ConnectionIds.Any())
{
User removeUser;
Users.TryRemove(userName, out removeUser);
}
}
}
return Clients.Group("admins").showUserCount(Users.Count(a => a.Value.IsRole != true));
}
else
{
return base.OnDisconnected(false);
}
}
} <script type="text/javascript">
var userHub = $.connection.userActivityHub;
$.connection.hub.logging = true;
$.connection.hub.start().done(function() {
userHub.server.join();
});
$(function() {
window.onbeforeunload = function() {
$.connection.hub.stop();
};
});
</script> <script type="text/javascript">
var userHub = $.connection.userActivityHub;
userHub.client.showUserCount = function (message) {
$('#userOnlineCount').html(message);
};
$.connection.hub.start().done(function() {
userHub.server.adminJoin().done(function() {
userHub.server.getUserCount();
});
});
</script> <script>
$('a.btn.btn-danger.btn-block').click(function(e) {
e.preventDefault();
$('#logoutForm').submit();
$.connection.userActivityHub.connection.stop();
});
$(function() {
window.onbeforeunload = function(e) {
$.connection.hub.stop();
};
});
</script> 
public static readonly ConcurrentDictionary<string, string> OnlineUsers =
new ConcurrentDictionary<string, string>();