SqlDependency se elimina después de que se activa el evento, por lo que debe ejecutar el comando nuevamente con la dependencia. A continuación se muestra un ejemplo de aplicación de consola que se suscribirá nuevamente a menos que la notificación se deba a un error.
using System;
using System.Data;
using System.Data.SqlClient;
namespace SqlDependencyExample
{
class Program
{
static string connectionString = @"Data Source=.;Initial Catalog=YourDatabase;Application Name=SqlDependencyExample;Integrated Security=SSPI";
static void Main(string[] args)
{
SqlDependency.Start(connectionString);
getDataWithSqlDependency();
Console.WriteLine("Waiting for data changes");
Console.WriteLine("Press enter to quit");
Console.ReadLine();
SqlDependency.Stop(connectionString);
}
static DataTable getDataWithSqlDependency()
{
using (var connection = new SqlConnection(connectionString))
using (var cmd = new SqlCommand("SELECT Col1, Col2, Col3 FROM dbo.MyTable;", connection))
{
var dt = new DataTable();
// Create dependency for this command and add event handler
var dependency = new SqlDependency(cmd);
dependency.OnChange += new OnChangeEventHandler(onDependencyChange);
// execute command to get data
connection.Open();
dt.Load(cmd.ExecuteReader(CommandBehavior.CloseConnection));
return dt;
}
}
// Handler method
static void onDependencyChange(object sender,
SqlNotificationEventArgs e)
{
Console.WriteLine($"OnChange Event fired. SqlNotificationEventArgs: Info={e.Info}, Source={e.Source}, Type={e.Type}.");
if ((e.Info != SqlNotificationInfo.Invalid)
&& (e.Type != SqlNotificationType.Subscribe))
{
//resubscribe
var dt = getDataWithSqlDependency();
Console.WriteLine($"Data changed. {dt.Rows.Count} rows returned.");
}
else
{
Console.WriteLine("SqlDependency not restarted");
}
}
}
}
