MSDN Magazine - June 2008 - (Page 26)

protected void Timer1_Tick(object sender, EventArgs e) { Label2.Text = " Last update: " + DateTime.Now.ToLocalTime(); GridView1.DataSource = picker.Update(); GridView1.DataBind(); } The picker object is an instance of a custom helper class named StockPicker. This class incorporates an instance of the service class in charge of retrieving quotes. Here’s the constructor of the StockPicker class: public StockPicker(string stocks) { string provider = ConfigurationManager.AppSettings["StockProvider"]; _service = GetFactory(serviceProvider, stocks); if (_service == null) return; _desc = _service.GetServiceDescription(); } The picker reads the name of the service provider class from the configuration file and instantiates it. The picker communicates with the service class through the contract represented by the IQuoteService interface: interface IQuoteService { StockInfoCollection GetQuotes(); string GetServiceDescription(); } The sample code accompanying this column uses a fake quote service that just returns random numbers in lieu of stock quotes. Figure 2 Live Quote Page Using Partial Rendering However, the page code can easily be configured to use a real-world quote service. All that you have to do is create a class that implements the IQuoteService interface and connect to a real stock data service. In the sample code, the bindable data is represented as a collection of StockInfo objects: public class StockInfo { public string Symbol { get; set; } public string Quote { get; set; } public string Change { get; set; } public string Day { get; set; } public string Time { get; set; } } Figure 2 shows a sample ASP.NET AJAX page that is based on this API in action. Limits of Partial Rendering Functionally speaking, the page in Figure 2 works as expected. If you’re OK with its performance and overall behavior, then you’re just fine. However, such a page has a few drawbacks worth noting, even if they won’t keep you up at night. First, the page moves quite a bit of data around each time it’s updated. The amount of data may not be problematic for a relatively scanty page like this that refreshes every 10 minutes. If you use Fiddler or Web Development Helper to monitor, you’ll see that the size of the payload is around 3KB in download and somewhat less in upload. Again, if you’re OK with these numbers, then by all means go for partial rendering. These numbers, though, lose much of their appeal if you look at the internal mechanics of the page. The view state of the page is sent back and forth for every update. The response contains both 26 msdn magazine Cutting Edge http://www.steema.com

Table of Contents Feed for the Digital Edition of MSDN Magazine - June 2008

MSDN Magazine - June 2008 Contents Toolbox CLR Inside Out Cutting Edge Patterns In Practice SAAS Concurrency Robotics Form Filler GUI Library Service Station Foundations Windows With C++ Concurrent Affairs Going Places { End Bracket }

MSDN Magazine - June 2008

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