Beginning ASP.NET 4.5 in CSharp and VB Opsylum

308 x CHAPTER 8 USER CONTROLS
This code first tries to get the value from View State using ViewState("NavigateUrl") in VB.NET or
ViewState["NavigateUrl"] in C#, which uses square brackets to access items in a collection. If the
value that is returned is Nothing or null, the getter returns the default value for the property: http://
p2p.wrox.com.
However, if the value is not Nothing, it is cast to a string using CType in VB.NET and (string) in C#
and eventually returned to the calling code. At the end, the NavigateUrl returned from the View State
property is assigned to the HRef property of the anchor tag again, which is then used as the URL users
are taken to when they click the image.
View State Considerations
Although View State is designed to overcome the problems of maintaining state as outlined in the
previous exercise, you should carefully consider whether or not you use it. The values you store in
View State are sent to the browser and back to the server on every request. When you store many
or large values in View State, this increases the size of the page and thus negatively impacts performance.
Never store large objects like database records in View State; it’s often quicker to get the
data fresh from the database on each request than passing it along in the hidden View State field if
the amount of data that needs to be stored is large. Also, because the View State is stored within
the page and is thus transferred over the wire, you shouldn’t use it to store sensitive values such as
passwords.
PRACTICAL TIPS ON USER CONTROLS
The following list provides some practical tips on working with user controls:
‰ Don’t overuse user controls. User controls are great for encapsulating repeating content, but
they also make it a little harder to manage your site because code and logic is contained in
multiple files. If you’re not sure if some content will be reused in another part of the site, start
by embedding it directly in the page. You can always move it to a separate user control later
if the need arises.
‰ Keep user controls focused on a single task. Don’t create a user control that is able to display
five different types of unrelated content with a property that determines what to display. This
makes the control difficult to maintain and use. Instead, create five lightweight controls and
use them appropriately.
‰ When you create user controls that contain styled markup, don’t hardcode style information
like the CssClass for the server controls contained in the user control. Instead, consider
creating separate CssClass properties on the user control, which are then used to set the
CssClass of your server controls. This improves the reusability of your user control, making
it easier to incorporate the control in different designs.