In ASP.NET 2.0 it is now possible to create asynchronous pages in a very simple and easy way.
It gives you a whole new abstraction layer on top of the managed thread pool that let’s any webpage take advantage of multithreading.
On high volume websites it means much higher performance. The single coolest thing about it is that you build the web pages as you normally would, but move some of the code into two separate methods.
That means that there is no real learning curve, because of the simplicity.
The only thing needed to make is the use of classes that have asynchronous methods.
It could be calling web services, doing database queries, creating a web request or many other things. In this example I’ve chosen a web request because it is the simplest to demo.
The page makes an asynchronous request to a website and writes the HTTP status code to the response stream.
First of all, we have to tell the page that is has to work in asynchronous mode. We do that by adding the Async=”true” attribute to the page declaration.
<%@ Page Language="C#" Async="true" CodeFile="asyncpage.aspx.cs" Inherits="asyncpage" %>
Then we just have to add two methods and register them in the Page_Load event handler.
using System.Net;
protected void Page_Load(object sender, EventArgs e)
{
AddOnPreRenderCompleteAsync(BeginGetAsyncData, EndGetAsyncData);
}
private HttpWebRequest _Request = (HttpWebRequest)WebRequest.Create("http://www.google.com");
private IAsyncResult BeginGetAsyncData(Object src, EventArgs args, AsyncCallback cb, Object state)
{
return _Request.BeginGetResponse(cb, state);
}
private void EndGetAsyncData(IAsyncResult ar)
{
using (HttpWebResponse response = (HttpWebResponse)_Request.EndGetResponse(ar))
{
Response.Write(response.StatusCode);
}
}
As you can see from the example, only very few extra lines of code is needed to make the page render asynchronously.
Even though they are far from alike, it reminds me of the BackgroundWorker in Windows Forms.
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Mads Kristensen currently works as a Senior Developer at Traceworks located
in Copenhagen, Denmark. Mads graduated from Copenhagen Technical Academy with a multimedia degree in
2003, but has been a professional developer since 2000. His main focus is on ASP.NET but is responsible for Winforms, Windows- and
web services in his daily work as well. A true .NET developer with great passion for the simple solution.
