Push Notifications using signalR in ASP.NET MVC

I'm still learning ASP.NET MVC architecture and if any of my questions parts seem awful, sorry for the inconvenience that happened.

I want to add push notifications to my ASP.NET MVC web application which I have never used before.

I followed this article: http://demo.dotnetawesome.com/push-notification-system-with-signalr

I'm using Entity Framework, and added the database connection string to my web.config file.

I used to create database connection via a class:

public class zSqlDb: DbContext 
{
    public zSqlDb(): base("Data Source=YEA-LAPTOP;Initial Catalog=db_ptweb;Integrated Security=True")
    {
    }
}

So in this article, he creates a class and there writes code to save data changes in the database.

This is the code:

using System;
using System.Collections.Generic;
using System.Configuration;
using System.Linq;
using System.Web;
using System.Data.SqlClient;
using Microsoft.AspNet.SignalR;
 
namespace PushNotification
{
    public class NotificationComponent
    {
        //Here we will add a function for register notification (will add sql dependency)
        public void RegisterNotification(DateTime currentTime)
        {
            string conStr = ConfigurationManager.ConnectionStrings["sqlConString"].ConnectionString;
            string sqlCommand = @"SELECT [ContactID],[ContactName],[ContactNo] from [dbo].[Contacts] where [AddedOn] > @AddedOn";

            //you can notice here I have added table name like this [dbo].[Contacts] with [dbo], it's mandatory when you use Sql Dependency
            using (SqlConnection con = new SqlConnection(conStr))
            {
                SqlCommand cmd = new SqlCommand(sqlCommand, con);
                cmd.Parameters.AddWithValue("@AddedOn", currentTime);

                if (con.State != System.Data.ConnectionState.Open)
                {
                    con.Open();
                }

                cmd.Notification = null;
                SqlDependency sqlDep = new SqlDependency(cmd);
                sqlDep.OnChange += sqlDep_OnChange;

                //we must have to execute the command here
                using (SqlDataReader reader = cmd.ExecuteReader())
                {
                    // nothing need to add here now
                }
            }
        }
 
        void sqlDep_OnChange(object sender, SqlNotificationEventArgs e)
        {
            //or you can also check => if (e.Info == SqlNotificationInfo.Insert) , if you want notification only for inserted record
            if (e.Type == SqlNotificationType.Change)
            {
                SqlDependency sqlDep = sender as SqlDependency;
                sqlDep.OnChange -= sqlDep_OnChange;
 
                //from here we will send notification message to client
                var notificationHub = GlobalHost.ConnectionManager.GetHubContext<NotificationHub>();
                notificationHub.Clients.All.notify("added");
                //re-register notification
                RegisterNotification(DateTime.Now);
            }
        }
 
        public List<Contact> GetContacts(DateTime afterDate)
        {
            using (MyPushNotificationEntities dc = new MyPushNotificationEntities())
            {
                return dc.Contacts.Where(a => a.AddedOn > afterDate).OrderByDescending(a => a.AddedOn).ToList();
            }
        }
    }
}

But I did to add records to the database by using the controller. So will this change the definition of the push notification process? If yes then I want to know how to match this code with mine.