Callback method on the SignalR Wpf client side - wpf

Question

I have 2 .NET solutions. One is asp.net mvc web application which is signalr server. The other is SignalR WPF client that consumes the collection of custom class objects from the web signalr server. I run the signalr MVC web server with IIS. The signalr WPF client application is run in another VS instance.
The SignalR web server has a Hub method (named "MessageLogHub", please see the below codes) that uses SqlDependency to broadcast collection of custom class objects to all signalr clients if there is a change (e.g. manually inserting data into the SQL Server database table) in a target database table. The collection of custom class objects are all of the records of a SQL Server database server.
From the signalr WPF client application side, I let the client register the SignalR server method as follows:
Proxy.On<List<MessageLog>>("BroadcastMessage", OnBroadcastMessage);
And the call back method named "OnBroadcastMessage" looks like:
private void OnBroadcastMessage(List<MessageLog> logs)
{
// problem: this callback method is hits once there is a put from signalr server. but the "logs" parameter's value is never changed !!!
Dispatcher.Invoke(() =>
{
textblockTime.Text = DateTime.Now.ToLongTimeString() + " - logs.Count=" + logs.Count();
datagridLogs.ItemsSource = null;
datagridLogs.ItemsSource = logs;
});
}
So when there is a change of database, the SignalR web server will calls the method "BroadcastMessage" on all connected clients (please see the below Signalr Hub server codes) and the callback method (on the SignalR WPF client codes) "OnBroadcastMessage" will be fired automatically on clients (WPF or web app clients). In VS, I debugs the call back method named "OnBroadcastMessage" and I see it is hit when there is a change in the database that triggers the SignalR server codes to broadcast to all connected clients.
The problem is in the signalr Wpf client callback method of "OnBroadcastMessage" (please see the above code of callback method of "OnBroadcastMessage"), the value of the "logs" parameter is not changed anytime the debug break-point is hit in that callback method. If a row is inserted in the database table, then the returned value of "logs" parameter is supposed to be changed and the new "logs" parameter is put to the signalr client side. Please help me.
I have another signalr asp.net MVC web project that is signalr client and it is embedded in the SignalR MVC web server solution. It works fine with the signalr server and I see the changes in real time way with that signalR web client. But the signalr WPF client application is not working as mentioned above.
Here are the codes (the xaml code behind file) for signalr WPF client application:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Windows;
using MessageWatchWpfClient.Models;
using Microsoft.AspNet.SignalR.Client;
namespace MessageWatchWpfClient
{
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
private string hostUrl = "http://localhost/MessageWatch/signalr";
public IHubProxy Proxy { get; set; }
public HubConnection Connection { get; set; }
public MainWindow()
{
InitializeComponent();
}
private async void Window_Loaded(object sender, RoutedEventArgs e)
{
try
{
Connection = new HubConnection(hostUrl);
Proxy = Connection.CreateHubProxy("MessageLogHub");
// 1) Register so that Server automatically calls Client when database is changed
Proxy.On<List<MessageLog>>("BroadcastMessage", OnBroadcastMessage);
await Connection.Start();
// 2) Client calls Server on the Wpf application loading and the following is run one time only
await Proxy.Invoke<List<MessageLog>>("GetAllMessagesLog")
.ContinueWith((t) =>
{
Dispatcher.Invoke(() =>
{
textblockTime.Text = DateTime.Now.ToLongTimeString() + " - logs.Count=" + t.Result.Count();
datagridLogs.ItemsSource = t.Result;
});
}
);
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
}
private void OnBroadcastMessage(List<MessageLog> logs)
{
// problem: this callback method is hits once there is a put from signalr server. but the "logs" parameter's value is never changed !!!
Dispatcher.Invoke(() =>
{
textblockTime.Text = DateTime.Now.ToLongTimeString() + " - logs.Count=" + logs.Count();
datagridLogs.ItemsSource = null;
datagridLogs.ItemsSource = logs;
});
}
}
}
The following codes are for SignalR Hub class on the server side application that is Asp.net MVC web and is hosted on IIS:
using System;
using System.Collections.Generic;
using System.Configuration;
using System.Data;
using System.Data.SqlClient;
using System.Globalization;
using MessageWatch.Models;
using Microsoft.AspNet.SignalR;
using SD = SignalR.Dal;
using MessageWatch.Utils;
namespace MessageWatch.Hubs
{
public class MessageLogHub : Hub
{
NLog.Logger _logger = NLog.LogManager.GetCurrentClassLogger();
public IEnumerable<MessageLog> GetAllMessagesLog()
{
var messageList = new List<MessageLog>();
try
{
var conStr = ConfigurationManager.ConnectionStrings["SignalRDatabase"].ToString();
var connection = new SqlConnection(conStr);
const string query = "SELECT Message,EventID,LL.Name as LogLevelID,OC.Name as OperationCodeID,ML.ServerName,ML.ComponentName,ML.SubComponentName FROM [dbo].[MessageLog] ML inner join [dbo].[LogLevel] LL on ML.LogLevelID = LL.ID inner join [dbo].[OperationCode] OC on ML.OperationCodeID = OC.ID order by ML.ID desc";
SqlDependency.Start(conStr); // to avoid error "When using SqlDependency without providing an options value, SqlDependency.Start() must be called prior to execution of a command added to the SqlDependency instance."
var command = new SqlCommand(query, connection);
var dependency = new SqlDependency(command);
//If Something will change in database and it will call dependency_OnChange method.
dependency.OnChange += dependency_OnChange;
connection.Open();
var da = new SqlDataAdapter(command);
var dt = new DataTable();
da.Fill(dt);
for (var i = 0; i < dt.Rows.Count; i++)
{
var ml = new MessageLog
{
Name = dt.Rows[i]["Message"].ToString(),
EventID = Convert.ToInt32(dt.Rows[i]["EventID"].ToString()),
LogLevelName = dt.Rows[i]["LogLevelID"].ToString(),
OperationCodeName = dt.Rows[i]["OperationCodeID"].ToString(),
ServerName = dt.Rows[i]["ServerName"].ToString(),
ComponentName = dt.Rows[i]["ComponentName"].ToString(),
SubComponentName = dt.Rows[i]["SubComponentName"].ToString()
};
messageList.Add(ml);
}
}
catch (Exception ex)
{
_logger.Error(CultureInfo.CurrentCulture, "{0}", ex.Message);
}
return messageList;
}
private void dependency_OnChange(object sender, SqlNotificationEventArgs e)
{
if (e.Type == SqlNotificationType.Change)
{
SendNotifications();
}
}
private void SendNotifications()
{
var messageList = GetAllMessagesLog();
IHubContext context = GlobalHost.ConnectionManager.GetHubContext<MessageLogHub>();
context.Clients.All.broadcastMessage(messageList);//Will update all the clients with message log.
}
public void CreateData()
{
try
{
IHubContext context = GlobalHost.ConnectionManager.GetHubContext<MessageLogHub>();
var dbContext = new SD.SignalREntities();
var repository = new SD.GenericRepository(dbContext);
var ml = new DataRandomer().Create();
repository.Add(ml);
dbContext.SaveChanges();
context.Clients.All.createData();
}
catch (Exception ex)
{
_logger.Error(CultureInfo.CurrentCulture, "{0}", ex.Message);
}
}
}
}