I am trying to detect if any changes been made to SQL table I'm working with. I need to specify the search by selecting specific records only, and for this reason I need to use string parameter. I understand that according to this MSDN document:
The statement must not contain conditional statements that cannot change and cannot return results (for example, WHERE 1=0)
Is there any way to include string parameter when using SqlDependency?
If it means something, I use SQL Server 2012 and VS 2010
Here is my code so far.
Code output: "The above notification query is not valid.":
using System.Data;
using System.Data.SqlClient;
namespace AutoRegSession
{
public partial class RoomActiveSession : Form
{
public Timer timer = new Timer(); //Timer to measure update times
public string SessionID; //String to hold selected sessionID
string ConnStr = "Data Source=DUZY;Initial Catalog=AutoRegSQL;Integrated Security=True";
SqlDependency dependency;
public RoomActiveSession()
{
SqlDependency.Start(ConnStr);
InitializeComponent();
}
private void btn_Exit_Click(object sender, EventArgs e)
{
SqlDependency.Stop(ConnStr);
timer.Enabled = false; //Disable timer
timer.Stop(); //Stop timer
Application.Exit(); //Close application
}
//Check for table updates every 3 seconds
private void timer_Tick(object sender, EventArgs e)
{
refreshDGV();
}
//SQL query that returns current/updated attendance result list for the given SessionID
public void refreshDGV()
{
DataTable queryResult = new DataTable();
SqlConnection MyConn = new SqlConnection(ConnStr); //Use connection string
string query = @"SELECT TagID, SessionID, ScanningTime" +
" FROM Attendance " +
" WHERE SessionID = @SessionID ";
SqlCommand command = new SqlCommand(query, MyConn);
command.Parameters.Add("SessionID", SqlDbType.Char).Value = SessionID;
//Create a dependency and associate it with the SqlCommand
SqlDependency dependency = new SqlDependency(command);
//Subscribe to the SqlDependency event
dependency.OnChange += new OnChangeEventHandler(OnDependencyChange);
SqlDataAdapter adapter = new SqlDataAdapter(command);
adapter.Fill(queryResult);
DGVSetDataSouce(queryResult);
}
//Handler method for SQL Dependecy
private void OnDependencyChange(object sender, SqlNotificationEventArgs eventArgs)
{
if (eventArgs.Info == SqlNotificationInfo.Invalid)
{
MessageBox.Show("The above notification query is not valid.");
}
else
{
MessageBox.Show("Notification Info: " + eventArgs.Info);
MessageBox.Show("Notification source: " + eventArgs.Source);
MessageBox.Show("Notification type: " + eventArgs.Type);
}
}
//Create and start the timer
public void SetTimer()
{
timer.Interval = 3000;
timer.Tick += new EventHandler(timer_Tick);
timer.Enabled = true;
timer.Start();
}
}
}