FIXED: Code updated that now works.
Trying to setup a websocket for a management dashboard where I need queries using count_big() fields and GROUP BY clauses. Standard recordset lists work great, but once I add the count_big() the websocket doesn't stop sending data. I have read this post about limitations and count_big() appears OK to use. TIA
using Microsoft.Web.WebSockets;
using System;
using System.Collections.Generic;
using System.Configuration;
using System.Data;
using System.Data.SqlClient;
using System.Linq;
using System.Net;
using System.Net.Http;
using System.Web;
using System.Web.Http;
namespace DatabaseChangeNotification.Controllers
{
public class DatabaseNotificationController : ApiController
{
public HttpResponseMessage Get()
{
HttpContext.Current.AcceptWebSocketRequest(new ChatWebSocketHandler());
return Request.CreateResponse(HttpStatusCode.SwitchingProtocols);
}
class ChatWebSocketHandler : Microsoft.Web.WebSockets.WebSocketHandler
{
public string wsData = null;
public SqlCommand gblCommand = null;
public ChatWebSocketHandler()
{
SetupNotifier();
}
protected void SetupNotifier()
{
using (var connection = new SqlConnection(ConfigurationManager.ConnectionStrings["DefaultConnection"].ConnectionString))
{
connection.Open();
// DO NOT USE any "*" in queries
// WHen using count the variable was converted to string. Got Data flood
//
// Testing count_big data type
// getString failed
//
using (SqlCommand command = new SqlCommand(@"select [address], count_big(*) as [CurrentTotal] from dbo.users where address = 'main st' group by address", connection))
{
command.Notification = null;
SqlDependency dependency = new SqlDependency(command);
dependency.OnChange += new OnChangeEventHandler(dependency_OnChange);
if (connection.State == ConnectionState.Closed)
{
connection.Open();
}
//SqlCommand gblCommand = command;
wsData = null;
using (SqlDataReader reader = command.ExecuteReader())
{
while (reader.Read())
{
/* MUST MATCH column count and column data type */
// wsData += reader.GetString(0) + " " + reader.GetString(1) + " " + reader.GetString(2);
/* THIS WORKS FOR GETTING NUMERIC VARIABLES */
wsData += reader.GetValue(0) + " " + int.Parse(reader.GetValue(1).ToString());
// wsData += reader.GetString(0) + "</br>"; //works but we get data flood and no numbers
}
// reader.Close();
}
_chatClients.Broadcast("data: " + wsData);
}
}
} //SetupNotifier
private static WebSocketCollection _chatClients = new WebSocketCollection();
public override void OnOpen()
{
_chatClients.Add(this);
} // OnOpen
public override void OnMessage(string msg)
{
} // OnMessage
private void dependency_OnChange(object sender, SqlNotificationEventArgs e)
{
if (e.Type != SqlNotificationType.Change)
{
_chatClients.Broadcast("Returning, not a change notification ");
return;
}
/*
* Must remove dependency. Only works once.
*/
SqlDependency dependency = sender as SqlDependency;
dependency.OnChange -= dependency_OnChange;
//reset for next message.
SetupNotifier();
} // dependency_OnChange
} // ChatWebSocketHandler
} // DatabaseNotificationController
}
NOTE: This was happening before code was fixed.
Web Socket returns infinite listing:
data: main st 1
data: main st 1
data: main st 1
data: main st 1
data: main st 1
data: main st 1
data: main st 1
data: main st 1
data: main st 1
data: main st 1
data: main st 1
data: main st 1
data: main st 1
data: main st 1
data: main st 1
data: main st 1
data: main st 1
data: main st 1
{ .....}
