Programming C#, Third Edition

The Screen-Scraper Application

The screen scraper application has only one job, to populate the table in the database, from which the ASP.NET application will display the relative rankings.

It works by reading through a set of XML files, which contain ISBNs of books that compete on various subjects (ASP.NET, C#, VB.NET). For example, the file CSharpISBN.xml is shown in Example 16-1. These XML files are maintained by hand; if you find a new C# title you want to track, you just make a new entry for that ISBN.

Example 16-1. CSharpISBN.xml

 <isbns>
  <isbn>193183654X</isbn> 
  <isbn>0130461334</isbn> 
  <isbn>1893115593</isbn> 
  <isbn>0130622214</isbn> 
  <isbn>1861007043</isbn> 
  <isbn>1861004982</isbn> 
  <isbn>0672320711</isbn> 
  <isbn>0596001819</isbn> 
  <isbn>0735612897</isbn> 
  <isbn>0735612900</isbn> 
  <isbn>0596003099</isbn> 
  <isbn>0596003765</isbn> 
  <isbn>0072133295</isbn> 
  <isbn>0672322358</isbn> 
  <isbn>0072193794</isbn> 
  <isbn>067232122X</isbn> 
  <isbn>1588801926</isbn> 
  <isbn>0672321521</isbn> 
  <isbn>0735615683</isbn> 
  <isbn>0201729555</isbn> 
  </isbns>

As each ISBN is read, the relevant values (title, publisher, rank) are found on the Amazon web site and stored in the database table. A simple listbox is then updated, as shown in Figure 16-3. As each book is recorded, its summary information is added to the listbox. Once all the books are recorded, the system becomes dormant while a timer ticks down the remaining time between sessions. You can force a new session by clicking the Now button. This UI was intentionally ...