Beginning ASP.NET 4.5 in CSharp and VB Opsylum

Handling Events x 563
background-image: url(Images/SortAscending.png);
}
The .GridViewHeaderStyle th selector then stops the background image from repeating, positions
the image near the top, and determines the background color and text alignment:
.GridViewHeaderStyle th, .GridViewPagerStyle
{
background-color: #BCD1FE;
background-repeat: no-repeat;
background-position: 0 5px;
text-align: left;
}
By moving your control style declarations to a separate skin file that in turn is part of a theme, you have
created a very flexible, maintainable solution. If you want to see how the new styles are applied, open
the source of the page in the browser using its View Source command. Instead of inline styles, the relevant
class attributes are applied. If you want to change the layout of all the GridView controls in the
Management section, all you need to do now is modify the relevant CSS in the Management.css file. If
you need to make changes to other styles, don’t forget to add them to the GridView.skin file first.
Obviously, you can still tweak the controls at the page level. Though the skin defines the global
look and feel of the GridView, you can still set individual properties on columns as you did with the
ItemStyle-Width in the Genres page.
Although styles, skins, and themes are powerful tools to style your web pages, you’ll find
that they are often an all-or-nothing solution. For example, if you create ItemStyle and
AlternatingItemStyle elements (rather than using jQuery as you just did), they are applied to each
and every row in the grid. What if you wanted to change the look and feel of just a few rows? Or
what if you wanted to change some rows based on the actual data that the row is holding? You see
how to accomplish conditional formatting and more, using event handling, in the following section.
HANDLING EVENTS
Previous chapters have covered how the ASP.NET controls can raise events. You learned how to handle
these events with event-handler code that you typically add to the page’s Code Behind file. For example,
you wrote code to handle a Button control’s Click event. Additionally, in the preceding chapter,
you learned how to react to various events — such as Inserting and Inserted — that happen just
prior to and after interaction with the database. However, most controls expose a lot more events.
A solid understanding of the various events that fire during a control’s life cycle and the order in
which they fire is important knowledge for an ASP.NET developer. Being able to hook into the control’s
life cycle, tweaking parts of the output as you go, enables you to create flexible, dynamic web
pages that do exactly what you want.
To gain an understanding of the various events and the order in which they fi re, the next section
explains the basic steps in the ASP.NET control life cycle. You won’t see every event that is fired in
the process, but instead you see the ones you are most likely to use. Later sections then show you
how to make use of these events to change the behavior of your web pages.