Silverlight 4 with (HTTP) Duplex and SQL Notifications

using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.Serialization;
using System.ServiceModel;
using System.ServiceModel.Web;
using System.Text;
using wcfDuplex.Classes;

using System.Data.SqlClient;
using System.Security.Permissions;
using System.Data;
using wcfDuplex.Model;

namespace wcfDuplex
{
    // NOTE: You can use the "Rename" command on the "Refactor" menu to change the class name "Service1" in code, svc and config file together.
    public class Duplex : IDuplexService
    {
        public void Connect(string id)
        {
            IDuplexServiceClient client = OperationContext.Current.GetCallbackChannel<IDuplexServiceClient>();
            TrainServiceRunner.Register(client);

           
        }


        List<Author> authors;

        public List<Author> GetEmployeeList(DateTime startDate, DateTime endDate)
        {
            authors = new List<Author>();

            

            //the connection string to your database
            // string connString = "Data Source=DEVELOPER-PC;Initial Catalog=dependencyDB;Integrated Security=True;Timeout=10";
            string connString = @"Data Source=SQLSVR2008\SQL2008;Initial Catalog=dependencyDB;Persist Security Info=True;User ID=NotificationsUser;Password=password";

            //the name of our stored procedure
            string proc = "SelectCredentialsWithinDOBRange";

            //first we need to check that the current user has the proper permissions,
            //otherwise display the error

            return authors;

            if (!CheckUserPermissions())
            {

                Author author = new Author();
                author.ID = 0;
                author.FirstName = "No";
                author.SecondName = "Permission";
                author.Address = "To Access DB";
                author.DOB = "12/12/2010";
                authors.Add(author);

                return authors;
            }

            

            //clear our ListView so the data isnt doubled up
            authors = new List<Author>();
            bool success = SqlDependency.Start(connString);

            using (SqlConnection sqlConn = new SqlConnection(connString))
            {
                using (SqlCommand sqlCmd = new SqlCommand())
                {

                    SqlParameter myParm1 = sqlCmd.Parameters.Add("@StartDate", SqlDbType.DateTime, 20);
                    myParm1.Value = "20/01/1960";
                    SqlParameter myParm2 = sqlCmd.Parameters.Add("@EndDate", SqlDbType.DateTime, 20);
                    myParm2.Value = "20/01/2022";

                    sqlCmd.Connection = sqlConn;
                    sqlCmd.Connection.Open();

                    //tell our command object what to execute
                    sqlCmd.CommandType = CommandType.StoredProcedure;
                    sqlCmd.CommandText = proc;
                    sqlCmd.Notification = null;

                    SqlDependency dependency = new SqlDependency(sqlCmd);
                    dependency.OnChange += new OnChangeEventHandler(dependency_OnDataChangedDelegate);

                    if (sqlConn.State != ConnectionState.Open) sqlConn.Open();

                    using (SqlDataReader reader = sqlCmd.ExecuteReader())
                    {
                        while (reader.Read())
                        {
                            Author author = new Author();
                            author.ID = reader.GetInt32(0);
                            author.FirstName = reader.GetString(1);
                            author.SecondName = reader.GetString(2);
                            author.Address = reader.GetString(3);
                            author.DOB = reader.GetDateTime(4).ToString();
                            authors.Add(author);
                        }
                    }
                }
                return authors;
            }
        }

        private bool CheckUserPermissions()
        {
            try
            {
                SqlClientPermission permissions = new SqlClientPermission(PermissionState.Unrestricted);

                //if we cann Demand() it will throw an exception if the current user doesnt have the proper permissions
                permissions.Demand();

                return true;
            }
            catch
            {
                return false;
            }
        }

        private void dependency_OnDataChangedDelegate(object sender, SqlNotificationEventArgs e)
        {
            List<Author> myAuthors = this.GetEmployeeList(DateTime.Now.AddYears(-20), DateTime.Now.AddYears(1));


          
            TrainServiceRunner.watcher_Changed(myAuthors);




            //this example is for only a single notification so now we remove the event handler from the dependency object
            SqlDependency dependency = sender as SqlDependency;
            dependency.OnChange -= new OnChangeEventHandler(dependency_OnDataChangedDelegate);
        }
       
    }
}