SQLDependency Onchange event always firing without data change - asp.net

Question

I'm using it on a console project.
.NET Framework: 4.5
In my test code, SQLDependency onChange always firing although there is no data changes in Database.
class Program
{
private static string _connStr;
static void Main(string[] args)
{
_connStr = "data source=xxx.xxx.xx.xx;User Id=xxx;Password=xxx; Initial Catalog=xxx";
SqlDependency.Start(_connStr);
UpdateGrid();
Console.Read();
}
private static void UpdateGrid()
{
using (SqlConnection connection = new SqlConnection(_connStr))
{
using (SqlCommand command = new SqlCommand("select msgdtl,msgid From NotifyMsg", connection))
{
command.CommandType = CommandType.Text;
connection.Open();
SqlDependency dependency = new SqlDependency(command);
dependency.OnChange += new OnChangeEventHandler(dependency_OnChange);
SqlDataReader sdr = command.ExecuteReader();
Console.WriteLine();
while (sdr.Read())
{
Console.WriteLine("msgdtl:{0}\t (msgid:{1})", sdr["msgdtl"].ToString(), sdr["msgid"].ToString());
}
sdr.Close();
}
}
}
private static void dependency_OnChange(object sender, SqlNotificationEventArgs e)
{
UpdateGrid();
}
when I start running, onChange event fires and never stop. But there is no change in my databse.

Answer 1

Try to check the SqlNotificationEventArgs object in the dependency_OnChnage method. It looks like you have an error there. I had the same SqlDependency behavior one time and the problem was solved by changing select msgdtl,msgid From NotifyMsg to select msgdtl,msgid From dbo.NotifyMsg (The dbo statement has been added).
But I should warn you: be careful using SqlDependency class - it has the problems with memory leaks. Hovewer, you can use an open source realization of the SqlDependency class - SqlDependencyEx. It uses a database trigger and native Service Broker notification to receive events about the table changes. This is an usage example:
int changesReceived = 0;
using (SqlDependencyEx sqlDependency = new SqlDependencyEx(
TEST_CONNECTION_STRING, TEST_DATABASE_NAME, TEST_TABLE_NAME))
{
sqlDependency.TableChanged += (o, e) => changesReceived++;
sqlDependency.Start();
// Make table changes.
MakeTableInsertDeleteChanges(changesCount);
// Wait a little bit to receive all changes.
Thread.Sleep(1000);
}
Assert.AreEqual(changesCount, changesReceived);
With SqlDependecyEx you are able to monitor INSERT, DELETE, UPDATE separately and receive actual changed data (xml) in the event args object. Hope this help.

Answer 2

there is a custom implementation of SqlDependency that report you the changed table records:
var _con= "data source=.; initial catalog=MyDB; integrated security=True";
static void Main()
{
using (var dep = new SqlTableDependency<Customer>(_con, "Customer"))
{
dep.OnChanged += Changed;
dep.Start();
Console.WriteLine("Press a key to exit");
Console.ReadKey();
dep.Stop();
}
}
static void Changed(object sender, RecordChangedEventArgs<Customer> e)
{
if (e.ChangeType != ChangeType.None)
{
for (var index = 0; index < e.ChangedEntities.Count; index++)
{
var changedEntity = e.ChangedEntities[index];
Console.WriteLine("DML operation: " + e.ChangeType);
Console.WriteLine("ID: " + changedEntity.Id);
Console.WriteLine("Name: " + changedEntity.Name);
Console.WriteLine("Surame: " + changedEntity.Surname);
}
}
}
Here is the link: [https://tabledependency.codeplex.com]