SQL Server Notifications - My OnChange does not fire

I would like to make use of SQL Server notifications to capture insert events at my database within a winforms app. I am attempting to use the SQLDependency object. The MSDN articles make this seem pretty straight forward. So I have created a little example application to give it a try. The event only seems to fire as I enter my application the first time(MessageBox appears).开发者_运维问答 Inserting data into the table does not raise the OnChange event it would seem. Can someone tell me what I'm missing? Thanks!

 public Main()
    {
        InitializeComponent();
        var check = EnoughPermission();
        SqlDependency.Stop(constr);
        SqlDependency.Start(constr);
        if(connection == null)
        {
            connection = new SqlConnection(constr);
        }
        if(command == null)
        {
            command = new SqlCommand("Select ID, ChatMessage FROM dbo.Chat",connection);
        }
        connection.Open();
        command.Notification = null;
        SqlDependency dependency = new SqlDependency(command);
        dependency.OnChange += new OnChangeEventHandler(dependency_OnChange);
        command.ExecuteReader();
    }





    private void dependency_OnChange(object sender, SqlNotificationEventArgs e)
    {
        MessageBox.Show("Change!");
    }

While I was working in the implementation of query notification, I got the exact problem. I checked all configurations, code pieces, and even TCP settings, but nothing helped. Then, I figured out the following query to run on database and it solved my problem. Maybe you can try it.

ALTER AUTHORIZATION ON DATABASE::[Your DB] TO sa;

Your first notification is the only notification you'll get. Query Notifications are not a subscription for changes, once a notification is fired it is also invalidate. You are supposed to re-submit a new notification subscription.

If your query is notified immedeatly it means you did not get a notification for a change, but one for an invalid query. Check the values of the SqlNotificationEventArgs argument you receive. Check the Info to be Insert/Update/Delete, check the Source to be Data, check the Type to be Change.

Have a look at the Watcher Application example to better understand how you are supposed to re-subscribe when notified. For a better understanding of how the Query Notifications work, see The Mysterious Notification.