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Archive for the ‘AJAX’ Category

ASP.NET SignalR and Ext.NET MessageBus

Posted by dariosantarelli on October 20, 2013


Most of the modern web applications provides real-time functionalities (“real-time web“) through a set of technologies and practices that enable users to receive information as soon as it is published by its authors, rather than requiring that they or their software check a source periodically for updates.  Moreover, in very scalable and complex architectures, server-side code execution is often asynchronous. Just for example, let’s think to a task-based UI which submits a command like “book a plane ticket” to a web service. The server-side command processing could be performed after some hours: for example, the command could be just enqueued to a command-bus to be processed later. In scenarios like that, the client can’t count on an updated read model just after sending the command. As a consequence, in order to receive a feedback as soon as possible, all the involved clients should poll the server until the command execution reaches a significant state (e.g. in progress, completed, canceled etc.) and the read model is updated, ready for queries.

Before WebSockets, the classic implementations of this kind of real-time features were not so easy and they used to adopt strategies like forever frame (see “Comet“) or periodic/long polling. Today, all the modern browsers and web servers fully support WebSockets and they can extabilish bi-directional and persistent communications, so that a client can receive content through a “push” action performed by the server. In the ASP.NET world, SignalR is a growing new library that uses WebSockets under the covers when it’s available, and gracefully fallbacks to other techniques and technologies when it isn’t, while the application code stays the same. SignalR also provides a very simple, high-level API for doing server-to-client RPC (call JavaScript functions in clients’ browsers from server-side code) in an ASP.NET application, as well as adding useful hooks for connection management, e.g. connect/disconnect events, grouping connections, authorization.

Developers that are currently using the Ext.NET component framework can take advantage on SignalR by combining it with the Ext.NET MessageBus component. The MessageBus provides a simple and robust client-side infrastructure to propagate notifications to listening UI components. The reference scenario I’m talking about in this post is represented in the figure below:


1. The client browser extabilishes a persistent connection to a server-side SignalR application hub. After that the client mantains a reference to an auto-generated hub proxy.
2. The Ext.NET UI components submits commands to the server.
3. At any time of the server-side command execution, the server can use the SignalR hub to push notification messages back to all the involved clients via RPC.
4. Any client receiving a SignalR message through the hub proxy redirects the message to the Ext.NET Message Bus
5. On the basis of the specific type of message, the Ext.NET UI components are updated through a message handler function. In fact, each Ext.NET component has a MessageBusListeners property (client side handlers of MessageBus client side events) and a MessageBusDirectEvents property (server side handlers of MessageBus client side events).

Let’s have a look to a minimalistic example implemented in an ASP.NET MVC web application. Here’s the view :

@using Ext.Net;
@using Ext.Net.MVC;
@{
    Layout = null;
    var X = Html.X();
}
<!DOCTYPE html>
<html>
    <head>        
        <title>SignalR and Ext.NET MessageBus example</title>
        @Scripts.Render("~/bundles/modernizr")
        @Scripts.Render("~/bundles/jquery")
        @Scripts.Render("~/bundles/jquery.signalR")
        <script src="@Url.Content("~/signalr/hubs")" type="text/javascript"></script>
    </head>
<body>
@(X.ResourceManager())
@(X.Viewport().Padding(20).Items()

.Add(X.Button().Icon(Icon.Add).Text("New customer")
      .DirectClickAction("AddCustomer", "Customers")) 

.Add(X.Button().Icon(Icon.Delete).Text("Delete customer")
      .DirectClickAction("DeleteCustomer", "Customers"))

.Add(X.GridPanel().Title("Customers").MarginSpec("10 0 0 0").Icon(Icon.User)
      .Store(X.Store()
              .AutoLoad(true)
              .Proxy(X.AjaxProxy().Url("/customers/all").Reader(X.JsonReader()))
              .Model(X.Model()
                      .Fields(fields =>
                      {
                        fields.Add(X.ModelField().Name("Id"));
                        fields.Add(X.ModelField().Name("Name"));
                        fields.Add(X.ModelField().Name("Surname"));
                        fields.Add(X.ModelField().Name("Email"));
                      })))
              .ColumnModel(columnModel =>
              {
                columnModel.Columns.Add(X.Column().Text("Name").DataIndex("Name").Flex(1));
                columnModel.Columns.Add(X.Column().Text("Surname").DataIndex("Surname").Flex(1));
                columnModel.Columns.Add(X.Column().Text("Email").DataIndex("Email").Flex(1));
              })
              .MessageBusListeners(new MessageBusListener 
              {   
                 Name = "Customers.*",
                 Handler = "this.getStore().reload();",
                 Buffer = 500
              }))

.Add(X.GridPanel().Title("Events log").MarginSpec("10 0 0 0").Icon(Icon.Report)
      .Store(X.Store()
      .Model(X.Model()
              .Fields(fields =>
                          {
                              fields.Add(X.ModelField().Name("EventId"));
                              fields.Add(X.ModelField().Name("DateTime"));
                              fields.Add(X.ModelField().Name("Name"));
                              fields.Add(X.ModelField().Name("Data"));
                          })))
                    .ColumnModel(columnModel =>
                    {
                        columnModel.Columns.Add(X.Column().Text("EventId").DataIndex("EventId").Flex(1));
                        columnModel.Columns.Add(X.Column().Text("DateTime").DataIndex("DateTime").Flex(1));
                        columnModel.Columns.Add(X.Column().Text("Event name").DataIndex("Name").Flex(1));
                        columnModel.Columns.Add(X.Column().Text("Event data").DataIndex("Data").Flex(1));
                    })
                    .MessageBusListeners(new MessageBusListener
                    {
                        Name = "Customers.*",
                        Handler = "this.getStore().add({ EventId: data.Id, DateTime: getFormattedDateTime(), 
                                   Name: name, Data: \"CustomerId: \" + data.CustomerId });"
})))
<script type="text/javascript">      
var loadHub = function () {
    var hubProxy = $.connection.applicationHub;
    hubProxy.client.publish = function (name, message) {
        Ext.net.Bus.publish(name, message);
    };
    $.connection.hub.start().done(function () {
        Ext.net.Notification.show({
            title: "Info",
            iconCls: "#Accept",
            html: "SignalR connection is active!"
        });
    });
};

$(document).ready(function () {
    loadHub();
});

</script>    
</body>
</html>

As you can see, the view is composed by the following Ext.NET components:

– A couple of buttons which send commands to the server (e.g. Add/Remove a customer)
– A grid panel which holds the current customer data
– A grid panel which holds trace data about messages received through the SignalR connection.

The integration between the client-side SignalR hub proxy and the Ext.NET components MessageBus is done through the loadHub javascript function: it wraps the SignalR hub named “applicationHub” so that all the received messages are redirected to the Ext.NET MessageBus and again to the listening UI components. Please note that the SignalR “publish” function and the Ext.NET MessageBus “publish” function accept the same parameters: the message name and the message data. For this reason, the integration between the two worlds is practically natural.

In the example above, the Store of the former GridPanel is reloaded each time its MessageBusListener intercepts any message whose name starts with the prefix “Customers.” . Please pay attention to the Buffer property: it’s very useful when the component is under message storming and we want the UI to be refreshed just after a specified delay during which no messages have been received.

What about server-side code? Well, the server-side code is not so relevant in this post. The most important thing to be considered here is that at some point of the server-side command execution, the code retrieves the SignalR hub, selects which clients will receive the RPC (for simplicity, in this example a message is sent to all connected clients) and finally pushes a message containing the data the client needs for updating UI. Here an example:

GlobalHost.ConnectionManager.GetHubContext<ApplicationHub>()
          .Clients.All.publish("Customers.Added", new CustomerAdded { ...<data for clients>... });

Useful links

Posted in .NET Framework, AJAX, ASP.NET, ASP.NET MVC, C#, Microsoft Technology, Programming, Web Development | Tagged: , , , , , , , | 1 Comment »

Experimenting with Ext.NET support for Razor: a GridPanel with AJAX proxy

Posted by dariosantarelli on June 2, 2012


In these days I’m having fun experimenting the Razor View Engine support introduced in Ext.NET v.2.0 (Beta3 at the time of writing) and I’m appreciating how fluently you can configure any Ext.NET component. Nowadays there isn’t a good documentation about these new features (on Ext.NET official site you can read “Server-side Ext.NET API documentation is being worked on”) so if you want more info about Razor support please have a look at the Ext.NET official forum (I’ve found this thread particularly helpful!). Moreover, in the Ext.NET Examples Explorer you can try to get the necessary knowledge for translating WebForms code examples into Razor views.
In this post I’d like to show one of my first tests: a simple GridPanel supporting server-side data paging via AJAX proxy.
Here the interesting Razor syntax:

@Html.X().ResourceManager()
@(Html.X().GridPanel()
        .Title("Customers")
        .Store(store => store.Add(Html.X().Store()
            .AutoLoad(true)
            .RemoteSort(false)
            .IsPagingStore(true)
            .RemotePaging(true)
            .PageSize(20)
            .Proxy(proxy => proxy.Add(Html.X().AjaxProxy()
                            .Url("/Customers/GetCustomers")
                            .Reader(reader => reader.Add(Html.X().JsonReader()
                                                                   .Root("data")
                                                                   .TotalProperty("total")
                                                                   .IDProperty("CustomerID")))))
            .Model(model => model.Add(Html.X().Model()
                        .Fields(fields =>
                        {
                            fields.Add(Html.X().ModelField().Name("CustomerID"));
                            fields.Add(Html.X().ModelField().Name("ContactName"));
                            fields.Add(Html.X().ModelField().Name("CompanyName"));
                            fields.Add(Html.X().ModelField().Name("Phone"));
                            fields.Add(Html.X().ModelField().Name("Fax"));
                            fields.Add(Html.X().ModelField().Name("Region"));
                        })))))
        .ColumnModel(columnModel =>
        {
            columnModel.Columns.Add(Html.X().Column().Text("ContactName").DataIndex("ContactName").Flex(1));
            columnModel.Columns.Add(Html.X().Column().Text("CompanyName").DataIndex("CompanyName").Flex(1));
            columnModel.Columns.Add(Html.X().Column().Text("Phone").DataIndex("Phone"));
            columnModel.Columns.Add(Html.X().Column().Text("Fax").DataIndex("Fax"));
            columnModel.Columns.Add(Html.X().Column().Text("Region").DataIndex("Region"));
        })
        .BottomBar(bar => bar.Add(Html.X().PagingToolbar()
                                          .DisplayInfo(true)
                                          .DisplayMsg("Displaying customers {0} - {1} of {2}")))
        .View(view => view.Add(Html.X().GridView())))

 

First of all, please note the Html.X() helper method. This is the entry point for configuring any Ext.NET component. As requisite for getting started, you can call the Html.X().ResourceManager() helper method. Like the counterpart of Ext.NET for WebForms, it automatically injects every script and stylesheet you need into your page. The output should be something like this:

<link type="text/css" rel="stylesheet" href="/extjs/resources/css/ext-all-gray-embedded-css/ext.axd?v=25767" />   
<link type="text/css" rel="stylesheet" href="/extnet/resources/extnet-all-embedded-css/ext.axd?v=25767" />
<script type="text/javascript" src="/extjs/ext-all-js/ext.axd?v=25767"></script>
<script type="text/javascript" src="/extnet/extnet-all-js/ext.axd?v=25767"></script> 

OK, now through the Html.X() helper you can start configuring the GridPanel. In my example I have an AjaxProxy which calls a controller action in order to get back some JSON data to bind to the GridPanel. Some point of interest:

  • start and limit are the two standard ExtJs querystring parameters sent by the proxy to the remote data source in order to tell it how to page data.
  • AjaxProxy can process the resulting JSON via a JsonReader. In particular, pay attention to the Root() and TotalProperty() methods. They tell the reader respectively which root property in the JSON response contains the data rows and which property contains the total results count. They are two fundamental info for the right grid rendering.

Finally, the controller action code:

public ActionResult GetCustomers(int start, int limit)
{
    IEnumerable dtoArray;
    int total;

    using (var unitOfWork = _unitOfWorkFactory.Create())
    {
        var customerRepository = _repositoryFactory.CreateCustomerRepository(unitOfWork);
        var customers = customerRepository.Query()
                                          .Skip(start)
                                          .Take(limit);

         dtoArray = (from customer in customers
                        select new
                                {
                                    customer.CustomerID,
                                    customer.CompanyName,
                                    customer.ContactName,
                                    customer.Phone,
                                    customer.Fax,
                                    customer.Region
                                }).ToArray();

         total = customerRepository.Query().Count();
    }

    return Json(new { data = dtoArray, total = total }, JsonRequestBehavior.AllowGet);
}

 

Posted in AJAX, ASP.NET, ASP.NET MVC, C#, Programming, Web Development | 8 Comments »

.NET 3.5 Enhancements Training Kit

Posted by dariosantarelli on April 16, 2008


I was looking for some resources in order to learning something more about the .NET 3.5 extensions… after a little search I’ve discovered that just few days ago Microsoft has published the .NET 3.5 Enhancements Training Kit:

The .NET Framework 3.5 Enhancements Training Kit includes presentations, hands-on labs, and demos. This content is designed to help you learn how to utilize the .NET 3.5 Enhancement features including: ASP.NET MVC, ASP.NET Dynamic Data, ASP.NET AJAX History, ASP.NET Silverlight controls, ADO.NET Data Services and ADO.NET Entity Framework.

What can I say… Happy download

Posted in .NET Framework, AJAX, ASP.NET, Microsoft Technology, Web 2.0, Web Development | Leave a Comment »

How to create an ASP.NET 3.5 and Silverlight-enabled demo application

Posted by dariosantarelli on August 21, 2007


Steve Marx has recorded a 15 minute screencast to give you an idea of what’s possible with all the new ASP.NET 3.5 and SilverLight releases that came out last week.

Highlights:

  • Searching and paging via ListView, DataPager, and LinqDataSource (all new ASP.NET controls with .NET 3.5).
  • Video player via the Media control in the ASP.NET Futures July CTP (uses Silverlight 1.0 RC).
  • Popup biographies and “more/less” collapsible details via the new .NET 3.5-compatible drop of the AJAX Control Toolkit.
  • Back/forward buttons support via the History control in the ASP.NET Futures July CTP.

Resources:

Posted in AJAX, ASP.NET, Microsoft Technology, Web Development | 3 Comments »

AjaxControlToolkit v1.0.10606: strange behaviour of the ModalPopupExtender Control with DropShadow

Posted by dariosantarelli on June 13, 2007


I’d like to signal a strange behaviour of the latest version of the ModalPopupExtender control that I’ve just noticed. Let’s suppose we have this scenario: two ModalPopupExtender with different TargetControlID but same PopupControlID and DropShadow=”true”. Well, with the latest version of the control, when you click on one of the two controls TargetControlID, the client-side framework throws the following exception:

“Sys.InvalidOperationException: Two components with the same id ‘<PopupControlID>$DropShadowBehaviour’ can’t be added to the application”

As you can notice immediately, it seems a problem concerning the DropShadow property of the ModalPopuExtender. In fact, if you set it to “false”, magically everything works fine. I’m very disappointed about this seeming bug because in the previous version of AjaxControlToolkit this control worked regularly in this simple scenario.

Posted in AJAX, Web Development | 1 Comment »

“How Do I?” with ASP.NET AJAX Videos

Posted by dariosantarelli on February 17, 2007


On this page you will find dozens of videos designed for all ASP.NET developers, from the novice to the professional. If you are new to ASP.NET, you can learn the basics of how to create dynamic web applications with ASP.NET 2.0 and Visual Web Developer 2005 Express Edition, using either Visual Basic or C#. If you have a bit of development experience, you will learn how to employ some of the great new features introduced in ASP.NET 2.0.  If you haven’t watched these videos before, I highly recommend checking them out.  They are short, focused, videos that drill in on a specific topic and are designed to help master common scenarios when using the product.

Posted in .NET Framework, AJAX, ASP.NET, Web Development | Leave a Comment »

ASP.NET AJAX v1.0 Released!!!

Posted by dariosantarelli on January 30, 2007


Finally, ASP.NET AJAX v1.0 Released!!!
This technology enable a developer to create next-generation interfaces with reusable AJAX components. Moreover, it enhances existing Web pages using powerful AJAX controls with support for all modern browsers such as IE, Firefox and Opera.
You can continue using Visual Studio 2005 to take your ASP.NET 2.0 sites to the next level and access remote services and data directly from the browser without writing complicated script.
Downloads:
ASP.NET AJAX consists of the two essential downloads shown below. In the ASP.NET AJAX Downloads Page You’ll also find related downloads on this page including the Futures CTP, the sample applications, and the Microsoft AJAX Library for development on non-Windows platforms.

  • ASP.NET 2.0 AJAX Extensions 1.0
  • ASP.NET AJAX Control Toolkit (a shared-source community project from CodePlex consisting of samples and components that make it easier to work with AJAX-enabled controls and extenders. The Control Toolkit provides both ready-to-run samples and a SDK to simplify creating custom ASP.NET AJAX controls and extenders. Make sure you install ASP.NET AJAX 1.0 first!)

Posted in .NET Framework, AJAX, ASP.NET, Programming, Web Development, Web Services | Leave a Comment »

Mojax beta Developer Network

Posted by dariosantarelli on December 26, 2006


Mojax is one of the worlds first Mobile AJAX Application Frameworks. Unlike traditional AJAX Web Frameworks, mojax Moblets do not run within a browser and are not subject to the availability and quality of a network connection. Also, unlike a web application running on a mobile device, a mojax moblet has access to lower level device features such as Camera API, Push Messaging, Bluetooth, Location Services, Contacts and more. mojax is currently in private beta. If you would like to join the beta please subscribe to our user group and give a brief description of what your interest is in mojax.

Posted in AJAX, Java Technology | Leave a Comment »

A Complete List of Ajax Tools

Posted by dariosantarelli on November 2, 2006


Ajax has really taken off over the last two years. With the advancement of Ajax, new frameworks, utilities, and software packages have been built to make the production of Ajax web sites much easier. I’ve found a list of these tools, and the only list you will ever need ;)!!!!

Posted in AJAX | 1 Comment »