C# 4 and .NET 4

Displaying output as an HTMl Page ❘ 643
}
wrq.BeginGetResponse(new AsyncCallback(OnResponse), wrq);
protected static void OnResponse(IAsyncResult ar)
{
WebRequest wrq = (WebRequest)ar.AsyncState;
WebResponse wrs = wrq.EndGetResponse(ar);
// read the response...
}
Notice that you can retrieve the original WebRequest object by passing the object as the second parameter
to BeginGetResponse(). The second parameter is an object reference known as the state parameter.
During the callback method, you can retrieve the same state object using the AsyncState property of
IAsyncResult.
disPlaying ouTPuT as an hTml Page
The examples so far in this chapter show how the .NET base classes make it very easy to download
and process data from the Internet. However, so far you have displayed files only as plain text. Quite
often, you will want to view an HTML file in an Internet Explorer-style interface in which the rendered
HTML allows you to see what the web document actually looks like. Unfortunately, there is no
.NET version of Microsoft’s Internet Explorer, but that does not mean that you cannot easily
accomplish this task.
Before the release of the .NET Framework 2.0, you could make reference to a Component Object Model
(COM) object that was an encapsulation of Internet Explorer and use the .NET-interop capabilities to have
aspects of your application work as a browser. Now, since the release of the .NET Framework 2.0, you can
use the built-in WebBrowser control available for your Windows Forms applications.
The WebBrowser control encapsulates the COM object even further for you and makes the tasks that were
once more complicated, even easier. In addition to the WebBrowser control, another option is to use the
programmatic ability to call up Internet Explorer instances from your code.
When not using the new WebBrowser control, you can programmatically start an Internet Explorer process
and navigate to a web page using the Process class in the System.Diagnostics namespace:
Process myProcess = new Process();
myProcess.StartInfo.FileName = "iexplore.exe";
myProcess.StartInfo.Arguments = "http://www.wrox.com";
myProcess.Start();
However, the preceding code launches Internet Explorer as a separate window. Your application has no
connection to the new window and therefore cannot control the browser.
Using the new WebBrowser control, however, allows you to display and control the browser as an integrated
part of your application. The new WebBrowser control is quite sophisticated, featuring a large number of
methods, properties, and events.
allowing simple Web browsing from your applications
For the sake of simplicity, start by creating a Windows Forms application that simply has a TextBox control
and a WebBrowser control. You will build the application so that the end user will simply enter a URL into
the text box and press Enter, and the WebBrowser control will do all the work of fetching the web page and
displaying the resulting document.
In Visual Studio 2010 Designer, your application should look like Figure 24-3.
www.it-ebooks.info