具有 SignalR 用户特定的 SqlDependency

Question

请关注代码：

_布局：

$(function () {
    var connection = $.connection.notificationHub;

    //signalr method for push server message to client
    connection.client.addNotification = function (who) {
        //send notification here
        console.info("Send Notification")
    };

    // Start hub
    $.connection.hub.start().done(function () {
        console.log("SignalR Started")
    });
});

Global.asax.cs：

public class Global : HttpApplication
{
    string con = ConfigurationManager.ConnectionStrings["sqlConString"].ConnectionString;
    protected void Application_Start()
    {
        AreaRegistration.RegisterAllAreas();
        FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
        RouteConfig.RegisterRoutes(RouteTable.Routes);
        BundleConfig.RegisterBundles(BundleTable.Bundles);

        //here in Application Start we will start Sql Dependency
        SqlDependency.Start(con);
    }

    protected void Session_Start(object sender, EventArgs e)
    {
        NotificationComponent NC = new NotificationComponent();
        var currentTime = DateTime.Now;
        HttpContext.Current.Session["LastUpdated"] = currentTime;
        NC.RegisterNotification(currentTime);
    }

    protected void Application_End()
    {
        //here we will stop Sql Dependency
        SqlDependency.Stop(con);
    }
}

控制器：

[HttpPost]
[ValidateAntiForgeryToken]
public ActionResult MyAction(string parameter)
{
    //Database Notification (Table - Contacts) -Add or Update
    ctx.SaveChanges();
}

NotificationHub：中心

private readonly static ConnectionMapping<string> _connections = new ConnectionMapping<string>();

public static void SendNotification(string who)
{
    IHubContext context = GlobalHost.ConnectionManager.GetHubContext<NotificationHub>();
    foreach (var connectionId in _connections.GetConnections(who))
    {
        var result = context.Clients.Client(connectionId);
        if (result != null)
        {
            result.addNotification(who);
        }
    }
}

Components.cs：

public void RegisterNotification(DateTime currentTime)
{
    string conStr = ConfigurationManager.ConnectionStrings["sqlConString"].ConnectionString;
    string sqlCommand = @"SELECT [ContactID],[ContactName],[ContactNo] from [dbo].[Contacts] where [AddedOn] > @AddedOn";
    //you can notice here I have added table name like this [dbo].[Contacts] with [dbo], its mendatory when you use Sql Dependency
    using (SqlConnection con = new SqlConnection(conStr))
    {
        SqlCommand cmd = new SqlCommand(sqlCommand, con);
        cmd.Parameters.AddWithValue("@AddedOn", currentTime);
        if (con.State != System.Data.ConnectionState.Open)
        {
            con.Open();
        }
        cmd.Notification = null;
        SqlDependency sqlDep = new SqlDependency(cmd);
        sqlDep.OnChange += sqlDep_OnChange;
        //we must have to execute the command here
        using (SqlDataReader reader = cmd.ExecuteReader())
        {
            // nothing need to add here now
        }
    }
}

//After code `ctx.SaveChanges()`, call the code below (50 times):
void SqlDep_OnChange(object sender, SqlNotificationEventArgs e) //<-- Here Problem
{

    //from here we will send notification message to client
    NotificationHub.SendNotification("User1586");
    //...

    //re-register notification
    RegisterNotification(DateTime.Now);

    //HERE -After this line "RegisterNotification(DateTime.Now);", it returns again to the line: "void SqlDep_OnChange(object sender, SqlNotificationEventArgs e)"
}

用户“User1586”正在接收多个通知。 "void SqlDep_OnChange(object sender, SqlNotificationEventArgs e)" 行重复了几次。 如果你有 50 个在线用户，在这条线上做 50 次：

void SqlDep_OnChange(object sender, SqlNotificationEventArgs e)

如果你有 1000 个在线用户，在这条线上做 1000 次：

void SqlDep_OnChange(object sender, SqlNotificationEventArgs e).

换句话说，用户“User1586”收到了多个通知。

我按照这里的例子：http://www.dotnetawesome.com/2016/05/push-notification-system-with-signalr.html

想法是在数据库更新后向特定用户发送通知。

有什么办法吗？

Answer 1

首先，Sql依赖并不知道哪些数据发生了变化。所以你应该在事件处理程序内部查询。如果您想发送与用户 ID 相对应的数据，并且专门针对一个用户，我建议您这样做；

事件处理程序

private void SqlDependency_OnChange(object sender, SqlNotificationEventArgs e)
{
    if (e.Info == SqlNotificationInfo.Insert)
    {
         RecordInfo info = GetLastInsertedRecord(); //Just a custom entity
          if(info.UserId > 0)
             NotificationHub.SendNotification(info.UserId);
    }
    RegisterNotification(DateTime.Now);
}

集线器

public static List<UserConnection> ListUser { get; set; }
public static void SendNotification(string who)
{
    IHubContext context = GlobalHost.ConnectionManager.GetHubContext<MyHub>();  
    // Get specific user from connected ones.
    string Id = ListUser.Find(x => x.UserId == who).ConnectionId;
    context.Clients.Client(Id).addNotification(who); // or another data
}
//Add every connected users to the list
public override Task OnConnected()
    {
        ListUser = new List<UserConnection>();
        var us = new UserConnection();
        us.UserId = Context.QueryString["UserId"];
        us.ConnectionId = Context.ConnectionId;
        ListUser.Add(us);

        return base.OnConnected();
    }

更新客户端

$(function () {
    var connection = $.connection.notificationHub;
    //Pass the userId here as querystring  
    $.connection.hub.qs = "UserId=" + $("#labelHoldsUserId").val();
    //signalr method for push server message to client
    connection.client.addNotification = function (who) {
        //send notification here
        console.log(who + " sends message");
    };

    // Start hub
    $.connection.hub.start().done(function () {
        console.log("SignalR Started")
    });
})

Answer 2

似乎 OnChange 处理程序和 SqlDependency 实例都只适用于一个事件。触发事件并取消订阅处理程序后，您需要将处理程序注册到新的 SqlDependency 对象。

请参阅此处的链接以获取完整详细信息：http://msdn.microsoft.com/en-us/library/a52dhwx7(v=vs.80).aspx