How to get notifications using signal r based on selected value on client browser

Question

Here is the code of server side i.e of NotificationHub where i intend to add some logic by which i get realtime update from database based on client send value from front end

public class NotificationHub : Hub
{

    /// <summary>
    /// This function will be called from client to get all the messages.
    /// </summary>
    /// <returns></returns>
    public IEnumerable<MessageLog> GetAllMessagesLogs(string hello="")
    {
        string conStr = "Data Source=xyz;Initial Catalog=SignalRDatabase;Trusted_Connection=true;";
        SqlConnection connection = new SqlConnection(conStr);

        string query = $"SELECT Message,EventID,LL.Name as LogLevelID,OC.Name as OperationCodeID,ML.ServerName,ML.ComponentName,ML.SubComponentName FROM [dbo].[MessageLog] ML" +
            " inner join [dbo].[LogLevel] LL on ML.LogLevelID = LL.ID" +
            " inner join [dbo].[OperationCode] OC on ML.OperationCodeID = OC.ID" +
            $" where ML.SubComponentName='{hello}'";
        SqlDependency.Start(conStr);
        SqlCommand command = new SqlCommand(query, connection);
        SqlDependency dependency = new SqlDependency(command);

        //If Something will change in database and it will call dependency_OnChange method.
        dependency.OnChange += new OnChangeEventHandler(dependency_OnChange);
        connection.Open();
        SqlDataAdapter da = new SqlDataAdapter(command);
        DataTable dt = new DataTable();
        da.Fill(dt);

        List<MessageLog> messageList = new List<MessageLog>();
        for (int i = 0; i < dt.Rows.Count; i++)
        {
            MessageLog ml = new MessageLog();
            ml.Name = dt.Rows[i]["Message"].ToString();
            ml.EventID = Convert.ToInt32(dt.Rows[i]["EventID"].ToString());
            ml.LogLevelName = dt.Rows[i]["LogLevelID"].ToString();
            ml.OperationCodeName = dt.Rows[i]["OperationCodeID"].ToString();
            ml.ServerName = dt.Rows[i]["ServerName"].ToString();
            ml.ComponentName = dt.Rows[i]["ComponentName"].ToString();
            ml.SubComponentName = dt.Rows[i]["SubComponentName"].ToString();
            messageList.Add(ml);
        }
        return messageList;

    }

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

            SendNotifications();
        }
    }
    private void SendNotifications()
    {
        IEnumerable<MessageLog> messageList = GetAllMessagesLogs();

        IHubContext context = GlobalHost.ConnectionManager.GetHubContext<NotificationHub>();
        if(messageList.Count()>0)
        context.Clients.All.broadcastMessage(messageList);//Will update all the clients with message log.

    }
}

and here is the client side code javascript for now i have passed hard coded string in method getAllMessagesLogs() which will obviously change and will be bound with some select change event on front end

 <script type="text/javascript">
    $(function () {
        $('#btnPause').click(function () {
            $('#hdnValue').val(0);
        });
        $('#btnResume').click(function () {
            $('#hdnValue').val(1);
        });
        var $messageTable = $('#messageTable');
        var $messageTableBody = $messageTable.find('tbody');
        // Declare a proxy to reference the hub.
        var ew = $.connection.notificationHub;
        //This method will fill all the Messages in case of any database change.
        ew.client.broadcastMessage = function (messageLogs) {
            // Html encode display name and message.
            var i = 0;
            if ($('#hdnValue').val() == 1) {
                $messageTableBody.empty();

                $.each(messageLogs, function () {
                    var encodedName = messageLogs[i].Name;
                    var encodedEvent = messageLogs[i].EventID;
                    var encodedLogLevel = messageLogs[i].LogLevelName;
                    var encodedOCode = messageLogs[i].OperationCodeName;
                    var encodedServerName = messageLogs[i].ServerName;
                    var encodedCompName = messageLogs[i].ComponentName;
                    var encodedSubCompName = messageLogs[i].SubComponentName;
                    if (encodedLogLevel == "Fatal") {
                        $messageTableBody.append('<tr style="background-color:Red"><td>' + encodedName + '</td><td>' + encodedEvent + '</td><td>' + encodedLogLevel + '</td><td>' + encodedOCode + '</td><td>' + encodedServerName + '</td><td>' + encodedCompName + '</td><td>' + encodedSubCompName + '</td></tr>');
                    }
                    if (encodedLogLevel == "Warning") {
                        $messageTableBody.append('<tr style="background-color:Yellow"><td>' + encodedName + '</td><td>' + encodedEvent + '</td><td>' + encodedLogLevel + '</td><td>' + encodedOCode + '</td><td>' + encodedServerName + '</td><td>' + encodedCompName + '</td><td>' + encodedSubCompName + '</td></tr>');
                    }
                    else {
                        $messageTableBody.append('<tr><td>' + encodedName + '</td><td>' + encodedEvent + '</td><td>' + encodedLogLevel + '</td><td>' + encodedOCode + '</td><td>' + encodedServerName + '</td><td>' + encodedCompName + '</td><td>' + encodedSubCompName + '</td></tr>');
                    }
                    i = i + 1;
                });
            }
        };

        //This is where i want to send parameters and on selected parameters i want to receive notification in future
        $.connection.hub.start().done(function () {

            ew.server.getAllMessagesLogs("well hello").done(function (messageLogs) {
                debugger;
                console.log(messageLogs)
                var i = 0;
                if ($('#hdnValue').val() == 1) {
                    $messageTableBody.empty();
                    $.each(messageLogs, function () {
                        var encodedName = messageLogs[i].Name;
                        var encodedEvent = messageLogs[i].EventID;
                        var encodedLogLevel = messageLogs[i].LogLevelName;
                        var encodedOCode = messageLogs[i].OperationCodeName;
                        var encodedServerName = messageLogs[i].ServerName;
                        var encodedCompName = messageLogs[i].ComponentName;
                        var encodedSubCompName = messageLogs[i].SubComponentName;
                        if (encodedLogLevel == "Fatal") {
                            $messageTableBody.append('<tr style="background-color:Red"><td>' + encodedName + '</td><td>' + encodedEvent + '</td><td>' + encodedLogLevel + '</td><td>' + encodedOCode + '</td><td>' + encodedServerName + '</td><td>' + encodedCompName + '</td><td>' + encodedSubCompName + '</td></tr>');
                        }
                        if (encodedLogLevel == "Warning") {
                            $messageTableBody.append('<tr style="background-color:Yellow"><td>' + encodedName + '</td><td>' + encodedEvent + '</td><td>' + encodedLogLevel + '</td><td>' + encodedOCode + '</td><td>' + encodedServerName + '</td><td>' + encodedCompName + '</td><td>' + encodedSubCompName + '</td></tr>');
                        }
                        else {
                            $messageTableBody.append('<tr><td>' + encodedName + '</td><td>' + encodedEvent + '</td><td>' + encodedLogLevel + '</td><td>' + encodedOCode + '</td><td>' + encodedServerName + '</td><td>' + encodedCompName + '</td><td>' + encodedSubCompName + '</td></tr>');
                        }
                        i = i + 1;
                    });
                }
            });
        });
    });

</script>

so what i want is that to subscribe to some database change event based on selected value from client browser